106

This number is a composite.

The sum of the first 106 digits of π is prime. [Sellers]

106²-(53²-2²) is prime, where 53 and 2 are prime factors of 106. [Bajpai]

106^106-105^105 is prime. [Dobb]

The first occurrence of over 100 successive non-semiprimes (5238280947-5238281052). [Luhn]

The smallest multidigit invertible semiprime. Note that it ends with the smallest single-digit invertible semiprime. [Capelle]

106!-601 is the only known prime of form n!-R(n), where R(n) is the reversal of n. [Loungrides]

The smallest Cyclops semiprime. [Gupta]