31331021 has 4 divisors (see below), whose sum is σ = 31342944. Its totient is φ = 31319100.

The previous prime is 31330993. The next prime is 31331023. The reversal of 31331021 is 12013313.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12013313 = 13 ⋅924101.

It is a cyclic number.

It is not a de Polignac number, because 31331021 - 2²² = 27136717 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31330987 and 31331005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31331023) 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, 95 + ... + 7916.

It is an arithmetic number, because the mean of its divisors is an integer number (7835736).

Almost surely, 2^31331021 is an apocalyptic number.

It is an amenable number.

31331021 is a deficient number, since it is larger than the sum of its proper divisors (11923).

31331021 is an equidigital number, since it uses as much as digits as its factorization.

31331021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11922.

The product of its (nonzero) digits is 54, while the sum is 14.

The square root of 31331021 is about 5597.4119912688. The cubic root of 31331021 is about 315.2522410609.

Adding to 31331021 its reverse (12013313), we get a palindrome (43344334).

The spelling of 31331021 in words is "thirty-one million, three hundred thirty-one thousand, twenty-one".