21391884 has 24 divisors (see below), whose sum is σ = 55460720. Its totient is φ = 7130592.

The previous prime is 21391871. The next prime is 21391889. The reversal of 21391884 is 48819312.

It is a super-2 number, since 2×21391884² = 915225402138912, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21391889) 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, 98929 + ... + 99144.

Almost surely, 2^21391884 is an apocalyptic number.

It is an amenable number.

21391884 is an abundant number, since it is smaller than the sum of its proper divisors (34068836).

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

21391884 is a wasteful number, since it uses less digits than its factorization.

21391884 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198086 (or 198078 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 21391884 is about 4625.1361061054. The cubic root of 21391884 is about 277.5980077481.

The spelling of 21391884 in words is "twenty-one million, three hundred ninety-one thousand, eight hundred eighty-four".