21693644 has 12 divisors (see below), whose sum is σ = 43387344. Its totient is φ = 9297264.

The previous prime is 21693641. The next prime is 21693667. The reversal of 21693644 is 44639612.

21693644 is an admirable number.

It is a super-2 number, since 2×21693644² = 941228379997472, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21693641) 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, 387359 + ... + 387414.

It is an arithmetic number, because the mean of its divisors is an integer number (3615612).

Almost surely, 2^21693644 is an apocalyptic number.

It is an amenable number.

21693644 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21693644 is a wasteful number, since it uses less digits than its factorization.

21693644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 774784 (or 774782 counting only the distinct ones).

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

The square root of 21693644 is about 4657.6436102390. The cubic root of 21693644 is about 278.8972099430.

The spelling of 21693644 in words is "twenty-one million, six hundred ninety-three thousand, six hundred forty-four".