21332664 has 24 divisors (see below), whose sum is σ = 57776160. Its totient is φ = 7110864.

The previous prime is 21332653. The next prime is 21332693. The reversal of 21332664 is 46623312.

It is a tau number, because it is divible by the number of its divisors (24).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 148072 + ... + 148215.

It is an arithmetic number, because the mean of its divisors is an integer number (2407340).

Almost surely, 2^21332664 is an apocalyptic number.

21332664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21332664 is an abundant number, since it is smaller than the sum of its proper divisors (36443496).

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

21332664 is a wasteful number, since it uses less digits than its factorization.

21332664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296299 (or 296292 counting only the distinct ones).

The product of its digits is 5184, while the sum is 27.

The square root of 21332664 is about 4618.7296954899. The cubic root of 21332664 is about 277.3416091486.

Adding to 21332664 its reverse (46623312), we get a palindrome (67955976).

The spelling of 21332664 in words is "twenty-one million, three hundred thirty-two thousand, six hundred sixty-four".