21731013 has 6 divisors (see below), whose sum is σ = 31389254. Its totient is φ = 14487336.

The previous prime is 21730991. The next prime is 21731029. The reversal of 21731013 is 31013712.

It can be written as a sum of positive squares in only one way, i.e., 14424804 + 7306209 = 3798^2 + 2703^2 .

It is not a de Polignac number, because 21731013 - 2²⁴ = 4953797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21731053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1207270 + ... + 1207287.

Almost surely, 2^21731013 is an apocalyptic number.

It is an amenable number.

21731013 is a deficient number, since it is larger than the sum of its proper divisors (9658241).

21731013 is a wasteful number, since it uses less digits than its factorization.

21731013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2414563 (or 2414560 counting only the distinct ones).

The product of its (nonzero) digits is 126, while the sum is 18.

The square root of 21731013 is about 4661.6534620240. The cubic root of 21731013 is about 279.0572588381.

Adding to 21731013 its reverse (31013712), we get a palindrome (52744725).

The spelling of 21731013 in words is "twenty-one million, seven hundred thirty-one thousand, thirteen".