21539900 has 18 divisors (see below), whose sum is σ = 46741800. Its totient is φ = 8615920.

The previous prime is 21539899. The next prime is 21539933. The reversal of 21539900 is 993512.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 107600 + ... + 107799.

Almost surely, 2^21539900 is an apocalyptic number.

21539900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21539900 is an abundant number, since it is smaller than the sum of its proper divisors (25201900).

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

21539900 is a wasteful number, since it uses less digits than its factorization.

21539900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215413 (or 215406 counting only the distinct ones).

The product of its (nonzero) digits is 2430, while the sum is 29.

The square root of 21539900 is about 4641.1097810761. The cubic root of 21539900 is about 278.2367942613.

The spelling of 21539900 in words is "twenty-one million, five hundred thirty-nine thousand, nine hundred".