21881388 has 24 divisors (see below), whose sum is σ = 53744320. Its totient is φ = 6909840.

The previous prime is 21881383. The next prime is 21881459. The reversal of 21881388 is 88318812.

It is not an unprimeable number, because it can be changed into a prime (21881383) 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, 47758 + ... + 48213.

Almost surely, 2^21881388 is an apocalyptic number.

It is an amenable number.

21881388 is an abundant number, since it is smaller than the sum of its proper divisors (31862932).

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

21881388 is a wasteful number, since it uses less digits than its factorization.

21881388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95997 (or 95995 counting only the distinct ones).

The product of its digits is 24576, while the sum is 39.

The square root of 21881388 is about 4677.7545895440. The cubic root of 21881388 is about 279.6994564326.

The spelling of 21881388 in words is "twenty-one million, eight hundred eighty-one thousand, three hundred eighty-eight".