21636664 has 16 divisors (see below), whose sum is σ = 46364400. Its totient is φ = 9272832.

The previous prime is 21636661. The next prime is 21636677. The reversal of 21636664 is 46663612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 193129 + ... + 193240.

It is an arithmetic number, because the mean of its divisors is an integer number (2897775).

Almost surely, 2^21636664 is an apocalyptic number.

It is an amenable number.

21636664 is an abundant number, since it is smaller than the sum of its proper divisors (24727736).

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

21636664 is a wasteful number, since it uses less digits than its factorization.

21636664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386382 (or 386378 counting only the distinct ones).

The product of its digits is 31104, while the sum is 34.

The square root of 21636664 is about 4651.5227614191. The cubic root of 21636664 is about 278.6528142907.

The spelling of 21636664 in words is "twenty-one million, six hundred thirty-six thousand, six hundred sixty-four".