21918918 has 16 divisors (see below), whose sum is σ = 50100480. Its totient is φ = 6262536.

The previous prime is 21918881. The next prime is 21919003. The reversal of 21918918 is 81981912.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 260898 + ... + 260981.

It is an arithmetic number, because the mean of its divisors is an integer number (3131280).

Almost surely, 2^21918918 is an apocalyptic number.

21918918 is an abundant number, since it is smaller than the sum of its proper divisors (28181562).

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

21918918 is a wasteful number, since it uses less digits than its factorization.

21918918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521891.

The product of its digits is 10368, while the sum is 39.

The square root of 21918918 is about 4681.7644109887. The cubic root of 21918918 is about 279.8592745226.

The spelling of 21918918 in words is "twenty-one million, nine hundred eighteen thousand, nine hundred eighteen".