21387918 has 16 divisors (see below), whose sum is σ = 43218000. Its totient is φ = 7055616.

The previous prime is 21387893. The next prime is 21387929. The reversal of 21387918 is 81978312.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17793 + ... + 18956.

It is an arithmetic number, because the mean of its divisors is an integer number (2701125).

Almost surely, 2^21387918 is an apocalyptic number.

21387918 is an abundant number, since it is smaller than the sum of its proper divisors (21830082).

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

21387918 is a wasteful number, since it uses less digits than its factorization.

21387918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36851.

The product of its digits is 24192, while the sum is 39.

The square root of 21387918 is about 4624.7073420920. The cubic root of 21387918 is about 277.5808513701.

The spelling of 21387918 in words is "twenty-one million, three hundred eighty-seven thousand, nine hundred eighteen".