21132864 has 84 divisors (see below), whose sum is σ = 63794640. Its totient is φ = 6670080.

The previous prime is 21132863. The next prime is 21132869. The reversal of 21132864 is 46823112.

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

It is not an unprimeable number, because it can be changed into a prime (21132863) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9979 + ... + 11909.

It is an arithmetic number, because the mean of its divisors is an integer number (759460).

Almost surely, 2^21132864 is an apocalyptic number.

21132864 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 21132864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31897320).

21132864 is an abundant number, since it is smaller than the sum of its proper divisors (42661776).

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

21132864 is a wasteful number, since it uses less digits than its factorization.

21132864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1968 (or 1955 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21132864 is about 4597.0494885307. The cubic root of 21132864 is about 276.4730388229.

Adding to 21132864 its reverse (46823112), we get a palindrome (67955976).

The spelling of 21132864 in words is "twenty-one million, one hundred thirty-two thousand, eight hundred sixty-four".