21644946 has 12 divisors (see below), whose sum is σ = 46897422. Its totient is φ = 7214976.

The previous prime is 21644939. The next prime is 21644947. The reversal of 21644946 is 64944612.

21644946 is a `hidden beast` number, since 2 + 1 + 644 + 9 + 4 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 18792225 + 2852721 = 4335^2 + 1689^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21644946.

It is not an unprimeable number, because it can be changed into a prime (21644947) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 601231 + ... + 601266.

Almost surely, 2^21644946 is an apocalyptic number.

21644946 is an abundant number, since it is smaller than the sum of its proper divisors (25252476).

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

21644946 is a wasteful number, since it uses less digits than its factorization.

21644946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1202505 (or 1202502 counting only the distinct ones).

The product of its digits is 41472, while the sum is 36.

The square root of 21644946 is about 4652.4129223447. The cubic root of 21644946 is about 278.6883636436.

Subtracting from 21644946 its sum of digits (36), we obtain a triangular number (21644910 = T₆₅₇₉).

The spelling of 21644946 in words is "twenty-one million, six hundred forty-four thousand, nine hundred forty-six".