21520538 has 32 divisors (see below), whose sum is σ = 37149840. Its totient is φ = 9262080.

The previous prime is 21520537. The next prime is 21520547. The reversal of 21520538 is 83502512.

It can be written as a sum of positive squares in 8 ways, for example, as 388129 + 21132409 = 623^2 + 4597^2 .

It is a Harshad number since it is a multiple of its sum of digits (26).

It is not an unprimeable number, because it can be changed into a prime (21520537) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79868 + ... + 80136.

Almost surely, 2^21520538 is an apocalyptic number.

21520538 is a deficient number, since it is larger than the sum of its proper divisors (15629302).

21520538 is a wasteful number, since it uses less digits than its factorization.

21520538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 482.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 21520538 is about 4639.0233886024. The cubic root of 21520538 is about 278.1534011816.

The spelling of 21520538 in words is "twenty-one million, five hundred twenty thousand, five hundred thirty-eight".