31916921 has 4 divisors (see below), whose sum is σ = 31953792. Its totient is φ = 31880052.

The previous prime is 31916897. The next prime is 31916947. The reversal of 31916921 is 12961913.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31916921 is a prime.

It is a super-2 number, since 2×31916921² = 2037379692240482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31912921) 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, 17105 + ... + 18878.

It is an arithmetic number, because the mean of its divisors is an integer number (7988448).

Almost surely, 2^31916921 is an apocalyptic number.

It is an amenable number.

31916921 is a deficient number, since it is larger than the sum of its proper divisors (36871).

31916921 is an equidigital number, since it uses as much as digits as its factorization.

31916921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36870.

The product of its digits is 2916, while the sum is 32.

The square root of 31916921 is about 5649.5062616126. The cubic root of 31916921 is about 317.2052229220.

The spelling of 31916921 in words is "thirty-one million, nine hundred sixteen thousand, nine hundred twenty-one".