# A 10 digit phone number using all 10 digits only once

**URL:** <https://boards.straightdope.com/t/a-10-digit-phone-number-using-all-10-digits-only-once/835767>\
**Category:** In My Humble Opinion\
**Created:** [June 19, 2019, 8:29pm UTC](https://boards.straightdope.com/t/a-10-digit-phone-number-using-all-10-digits-only-once/835767 "2019-06-19T20:29:26Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\
**Post date:** [June 25, 2019, 3:41pm UTC](https://boards.straightdope.com/t/a-10-digit-phone-number-using-all-10-digits-only-once/835767/21 "2019-06-25T15:41:13Z")

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I’m close!!!

The 5 is used twice, and I lack a 9.

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**Author:** ![yendis](https://avatars.discourse-cdn.com/v4/letter/y/ed8c4c/32.png) [@yendis](https://boards.straightdope.com/u/yendis)\
**Post date:** [June 26, 2019, 12:17pm UTC](https://boards.straightdope.com/t/a-10-digit-phone-number-using-all-10-digits-only-once/835767/22 "2019-06-26T12:17:11Z")

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My parents home number is very close, with the 2 repeating in the last four digits. swap the 2 with a 9 and it’ll work and still be a valid number.

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**Author:** ![StusBlues](https://avatars.discourse-cdn.com/v4/letter/s/dc4da7/32.png) [@StusBlues](https://boards.straightdope.com/u/StusBlues)\
**Post date:** [June 26, 2019, 7:21pm UTC](https://boards.straightdope.com/t/a-10-digit-phone-number-using-all-10-digits-only-once/835767/23 "2019-06-26T19:21:53Z")

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I don’t recall seeing this, and probably would not have noticed, but the topic got me to thinking about the “rules” of the village where I grew up. The entire village was served by one prefix in the 1970s-80s, and the last four digits began with the same number for almost everyone I knew. (I recall dimly that there may have been one exception.) Given these rules, it is interesting that practically every phone number in town started with the same seven digits, none of which were repeated. It stands to reason that at least one or two people in town had phone numbers that were some combination of the set seven-digit root and the remaining three digits.

Banal observation: during this era, one could effectively dial just the last five digits of the phone number and contact their party. In my father’s day, one only needed to dial the last four. Made it easier for young kids to learn their phone numbers, I reckon.

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