21391584 has 48 divisors (see below), whose sum is σ = 56391552. Its totient is φ = 7100288.

The previous prime is 21391583. The next prime is 21391603. The reversal of 21391584 is 48519312.

It is a tau number, because it is divible by the number of its divisors (48).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391583) 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, 42277 + ... + 42779.

It is an arithmetic number, because the mean of its divisors is an integer number (1174824).

Almost surely, 2^21391584 is an apocalyptic number.

21391584 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21391584 is an abundant number, since it is smaller than the sum of its proper divisors (34999968).

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

21391584 is a wasteful number, since it uses less digits than its factorization.

21391584 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 959 (or 951 counting only the distinct ones).

The product of its digits is 8640, while the sum is 33.

The square root of 21391584 is about 4625.1036745137. The cubic root of 21391584 is about 277.5967100630.

The spelling of 21391584 in words is "twenty-one million, three hundred ninety-one thousand, five hundred eighty-four".