21267664 has 40 divisors (see below), whose sum is σ = 45309600. Its totient is φ = 9590400.

The previous prime is 21267619. The next prime is 21267679. The reversal of 21267664 is 46676212.

It is a Smith number, since the sum of its digits (34) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25819 + ... + 26629.

It is an arithmetic number, because the mean of its divisors is an integer number (1132740).

Almost surely, 2^21267664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21267664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22654800).

21267664 is an abundant number, since it is smaller than the sum of its proper divisors (24041936).

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

21267664 is a wasteful number, since it uses less digits than its factorization.

21267664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 979 (or 973 counting only the distinct ones).

The product of its digits is 24192, while the sum is 34.

The square root of 21267664 is about 4611.6877604625. The cubic root of 21267664 is about 277.0596386595.

It can be divided in two parts, 212 and 67664, that added together give a palindrome (67876).

The spelling of 21267664 in words is "twenty-one million, two hundred sixty-seven thousand, six hundred sixty-four".