21706644 has 12 divisors (see below), whose sum is σ = 50648864. Its totient is φ = 7235544.

The previous prime is 21706639. The next prime is 21706693. The reversal of 21706644 is 44660712.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 904432 + ... + 904455.

Almost surely, 2^21706644 is an apocalyptic number.

It is an amenable number.

21706644 is an abundant number, since it is smaller than the sum of its proper divisors (28942220).

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

21706644 is a wasteful number, since it uses less digits than its factorization.

21706644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1808894 (or 1808892 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 30.

The square root of 21706644 is about 4659.0389566948. The cubic root of 21706644 is about 278.9529088955.

The spelling of 21706644 in words is "twenty-one million, seven hundred six thousand, six hundred forty-four".