# 7

This number is a prime.

Single Curio View: (Seek other curios for this number)

A Mersenne prime (2^{p}- 1) with exponent

*p*= 3. The key prime factor of the perfect number 28. There are twenty-eight 3-digit numbers with digits summing to 7 (e.g., 601; 412) among which exactly 7 (e.g., 241; 313) are prime and also among which one (511) is of the form 2

^{q}- 1 where

*q*= 3 * 3. The seven 3-digit primes sum to 2281, a prime with an embedded "28" and with first and last digits summing to 3. Note that the number 2281 is also the exponent of the 17th Mersenne prime.

Submitted: 2001-11-08 10:43:54; Last Modified: 2009-09-14 10:39:06.

Printed from the PrimePages <primes.utm.edu> © G. L. Honaker and Chris K. Caldwell