21512644 has 6 divisors (see below), whose sum is σ = 37647134. Its totient is φ = 10756320.

The previous prime is 21512609. The next prime is 21512653. The reversal of 21512644 is 44621512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21511044 + 1600 = 4638^2 + 40^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2689077 + ... + 2689084.

Almost surely, 2^21512644 is an apocalyptic number.

It is an amenable number.

21512644 is a deficient number, since it is larger than the sum of its proper divisors (16134490).

21512644 is a wasteful number, since it uses less digits than its factorization.

21512644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5378165 (or 5378163 counting only the distinct ones).

The product of its digits is 1920, while the sum is 25.

The square root of 21512644 is about 4638.1724849341. The cubic root of 21512644 is about 278.1193869843.

The spelling of 21512644 in words is "twenty-one million, five hundred twelve thousand, six hundred forty-four".