21031504 has 20 divisors (see below), whose sum is σ = 43883476. Its totient is φ = 9706752.

The previous prime is 21031487. The next prime is 21031529. The reversal of 21031504 is 40513012.

It can be written as a sum of positive squares in 2 ways, for example, as 1317904 + 19713600 = 1148^2 + 4440^2 .

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 50349 + ... + 50764.

Almost surely, 2^21031504 is an apocalyptic number.

It is an amenable number.

21031504 is an abundant number, since it is smaller than the sum of its proper divisors (22851972).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21031504 is a wasteful number, since it uses less digits than its factorization.

21031504 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101134 (or 101128 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21031504 is about 4586.0117749522. The cubic root of 21031504 is about 276.0303124307.

Adding to 21031504 its reverse (40513012), we get a palindrome (61544516).

The spelling of 21031504 in words is "twenty-one million, thirty-one thousand, five hundred four".