21164664 has 64 divisors (see below), whose sum is σ = 55987200. Its totient is φ = 6656384.

The previous prime is 21164659. The next prime is 21164681. The reversal of 21164664 is 46646112.

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 15 ways as a sum of consecutive naturals, for example, 32389 + ... + 33035.

It is an arithmetic number, because the mean of its divisors is an integer number (874800).

Almost surely, 2^21164664 is an apocalyptic number.

21164664 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 21164664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27993600).

21164664 is an abundant number, since it is smaller than the sum of its proper divisors (34822536).

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

21164664 is a wasteful number, since it uses less digits than its factorization.

21164664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732 (or 728 counting only the distinct ones).

The product of its digits is 6912, while the sum is 30.

The square root of 21164664 is about 4600.5069285895. The cubic root of 21164664 is about 276.6116449994.

The spelling of 21164664 in words is "twenty-one million, one hundred sixty-four thousand, six hundred sixty-four".