21288618 has 24 divisors (see below), whose sum is σ = 49673988. Its totient is φ = 6550272.

The previous prime is 21288601. The next prime is 21288623. The reversal of 21288618 is 81688212.

It can be written as a sum of positive squares in 2 ways, for example, as 17114769 + 4173849 = 4137^2 + 2043^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 45255 + ... + 45722.

Almost surely, 2^21288618 is an apocalyptic number.

21288618 is an abundant number, since it is smaller than the sum of its proper divisors (28385370).

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

21288618 is a wasteful number, since it uses less digits than its factorization.

21288618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90998 (or 90995 counting only the distinct ones).

The product of its digits is 12288, while the sum is 36.

The square root of 21288618 is about 4613.9590375295. The cubic root of 21288618 is about 277.1505999436.

The spelling of 21288618 in words is "twenty-one million, two hundred eighty-eight thousand, six hundred eighteen".