21537420 has 48 divisors (see below), whose sum is σ = 60516960. Its totient is φ = 5723136.

The previous prime is 21537391. The next prime is 21537427. The reversal of 21537420 is 2473512.

It is not an unprimeable number, because it can be changed into a prime (21537427) 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, 25566 + ... + 26394.

It is an arithmetic number, because the mean of its divisors is an integer number (1260770).

Almost surely, 2^21537420 is an apocalyptic number.

21537420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21537420 is an abundant number, since it is smaller than the sum of its proper divisors (38979540).

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

21537420 is a wasteful number, since it uses less digits than its factorization.

21537420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1274 (or 1272 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21537420 is about 4640.8425959086. The cubic root of 21537420 is about 278.2261155715.

The spelling of 21537420 in words is "twenty-one million, five hundred thirty-seven thousand, four hundred twenty".