21694644 has 36 divisors (see below), whose sum is σ = 55334916. Its totient is φ = 7166208.

The previous prime is 21694633. The next prime is 21694657. The reversal of 21694644 is 44649612.

21694644 is a `hidden beast` number, since 2 + 1 + 6 + 9 + 4 + 644 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 11696400 + 9998244 = 3420^2 + 3162^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is a junction number, because it is equal to n+sod(n) for n = 21694599 and 21694608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1402 + ... + 6734.

It is an arithmetic number, because the mean of its divisors is an integer number (1537081).

Almost surely, 2^21694644 is an apocalyptic number.

It is an amenable number.

21694644 is an abundant number, since it is smaller than the sum of its proper divisors (33640272).

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

21694644 is a wasteful number, since it uses less digits than its factorization.

21694644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5456 (or 5451 counting only the distinct ones).

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

The square root of 21694644 is about 4657.7509594224. The cubic root of 21694644 is about 278.9014952677.

The spelling of 21694644 in words is "twenty-one million, six hundred ninety-four thousand, six hundred forty-four".