21437664 has 48 divisors (see below), whose sum is σ = 56827008. Its totient is φ = 7075712.

The previous prime is 21437639. The next prime is 21437701. The reversal of 21437664 is 46673412.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9229 + ... + 11315.

It is an arithmetic number, because the mean of its divisors is an integer number (1183896).

Almost surely, 2^21437664 is an apocalyptic number.

21437664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21437664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28413504).

21437664 is an abundant number, since it is smaller than the sum of its proper divisors (35389344).

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

21437664 is a wasteful number, since it uses less digits than its factorization.

21437664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2207 (or 2199 counting only the distinct ones).

The product of its digits is 24192, while the sum is 33.

The square root of 21437664 is about 4630.0825046645. The cubic root of 21437664 is about 277.7958924838.

The spelling of 21437664 in words is "twenty-one million, four hundred thirty-seven thousand, six hundred sixty-four".