21555118 has 16 divisors (see below), whose sum is σ = 34922160. Its totient is φ = 9919296.

The previous prime is 21555113. The next prime is 21555179. The reversal of 21555118 is 81155512.

It is a super-2 number, since 2×21555118² = 929246223987848, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555113) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9621 + ... + 11647.

It is an arithmetic number, because the mean of its divisors is an integer number (2182635).

Almost surely, 2^21555118 is an apocalyptic number.

21555118 is a deficient number, since it is larger than the sum of its proper divisors (13367042).

21555118 is a wasteful number, since it uses less digits than its factorization.

21555118 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2451.

The product of its digits is 2000, while the sum is 28.

The square root of 21555118 is about 4642.7489701684. The cubic root of 21555118 is about 278.3023038624.

The spelling of 21555118 in words is "twenty-one million, five hundred fifty-five thousand, one hundred eighteen".