21388888 has 32 divisors (see below), whose sum is σ = 41524560. Its totient is φ = 10321920.

The previous prime is 21388883. The next prime is 21388891. The reversal of 21388888 is 88888312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388883) 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, 33048 + ... + 33688.

Almost surely, 2^21388888 is an apocalyptic number.

It is an amenable number.

21388888 is a deficient number, since it is larger than the sum of its proper divisors (20135672).

21388888 is a wasteful number, since it uses less digits than its factorization.

21388888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 787 (or 783 counting only the distinct ones).

The product of its digits is 196608, while the sum is 46.

The square root of 21388888 is about 4624.8122124039. The cubic root of 21388888 is about 277.5850476545.

It can be divided in two parts, 2138 and 8888, that added together give a triangular number (11026 = T₁₄₈).

The spelling of 21388888 in words is "twenty-one million, three hundred eighty-eight thousand, eight hundred eighty-eight".