21310631 has 4 divisors (see below), whose sum is σ = 21886632. Its totient is φ = 20734632.

The previous prime is 21310613. The next prime is 21310637. The reversal of 21310631 is 13601312.

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

It is a cyclic number.

It is not a de Polignac number, because 21310631 - 2¹⁸ = 21048487 is a prime.

It is a super-2 number, since 2×21310631² = 908285987236322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21310637) 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, 287945 + ... + 288018.

It is an arithmetic number, because the mean of its divisors is an integer number (5471658).

Almost surely, 2^21310631 is an apocalyptic number.

21310631 is a deficient number, since it is larger than the sum of its proper divisors (576001).

21310631 is an equidigital number, since it uses as much as digits as its factorization.

21310631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 576000.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 21310631 is about 4616.3438996678. The cubic root of 21310631 is about 277.2460940793.

Adding to 21310631 its reverse (13601312), we get a palindrome (34911943).

It can be divided in two parts, 2 and 1310631, that multiplied together give a palindrome (2621262).

The spelling of 21310631 in words is "twenty-one million, three hundred ten thousand, six hundred thirty-one".