21636944 has 40 divisors (see below), whose sum is σ = 48711168. Its totient is φ = 9118080.

The previous prime is 21636943. The next prime is 21636949. The reversal of 21636944 is 44963612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636943) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5249 + ... + 8415.

Almost surely, 2^21636944 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 21636944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24355584).

21636944 is an abundant number, since it is smaller than the sum of its proper divisors (27074224).

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

21636944 is a wasteful number, since it uses less digits than its factorization.

21636944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3243 (or 3237 counting only the distinct ones).

The product of its digits is 31104, while the sum is 35.

The square root of 21636944 is about 4651.5528589924. The cubic root of 21636944 is about 278.6540163006.

The spelling of 21636944 in words is "twenty-one million, six hundred thirty-six thousand, nine hundred forty-four".