21538908 has 18 divisors (see below), whose sum is σ = 54445664. Its totient is φ = 7179624.

The previous prime is 21538903. The next prime is 21538939. The reversal of 21538908 is 80983512.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 598303 = 21538908 / (2 + 1 + 5 + 3 + 8 + 9 + 0 + 8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538903) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 299116 + ... + 299187.

Almost surely, 2^21538908 is an apocalyptic number.

It is an amenable number.

21538908 is an abundant number, since it is smaller than the sum of its proper divisors (32906756).

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

21538908 is a wasteful number, since it uses less digits than its factorization.

21538908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 598313 (or 598308 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 21538908 is about 4641.0029088549. The cubic root of 21538908 is about 278.2325228837.

The spelling of 21538908 in words is "twenty-one million, five hundred thirty-eight thousand, nine hundred eight".