91212131 has 4 divisors (see below), whose sum is σ = 92019432. Its totient is φ = 90404832.

The previous prime is 91212109. The next prime is 91212139. The reversal of 91212131 is 13121219.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-91212131 is a prime.

It is a super-2 number, since 2×91212131² = 16639305683122322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (91212139) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 403481 + ... + 403706.

It is an arithmetic number, because the mean of its divisors is an integer number (23004858).

Almost surely, 2^91212131 is an apocalyptic number.

91212131 is a deficient number, since it is larger than the sum of its proper divisors (807301).

91212131 is a wasteful number, since it uses less digits than its factorization.

91212131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 807300.

The product of its digits is 108, while the sum is 20.

The square root of 91212131 is about 9550.5042275264. The cubic root of 91212131 is about 450.1433798256.

The spelling of 91212131 in words is "ninety-one million, two hundred twelve thousand, one hundred thirty-one".