21538524 has 48 divisors (see below), whose sum is σ = 60818688. Its totient is φ = 5791488.

The previous prime is 21538523. The next prime is 21538547. The reversal of 21538524 is 42583512.

21538524 = T₂₈₁ + T₂₈₂ + ... + T₅₃₂.

It is a junction number, because it is equal to n+sod(n) for n = 21538491 and 21538500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538523) 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, 6114 + ... + 8969.

It is an arithmetic number, because the mean of its divisors is an integer number (1267056).

Almost surely, 2^21538524 is an apocalyptic number.

It is an amenable number.

21538524 is an abundant number, since it is smaller than the sum of its proper divisors (39280164).

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

21538524 is a wasteful number, since it uses less digits than its factorization.

21538524 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15114 (or 15112 counting only the distinct ones).

The product of its digits is 9600, while the sum is 30.

The square root of 21538524 is about 4640.9615383022. The cubic root of 21538524 is about 278.2308694121.

The spelling of 21538524 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred twenty-four".