99969

+ The largest five-digit composite number ending in 1, 3, 7, or 9 that yields no primes if the first digit is changed. I.e., 9969, 19969, 29969, 39969, 49969, 59969, 69969, 79969 and 89969 are all composite numbers.

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