21317644 has 18 divisors (see below), whose sum is σ = 37973684. Its totient is φ = 10471320.

The previous prime is 21317627. The next prime is 21317651. The reversal of 21317644 is 44671312.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 13159 + ... + 14689.

Almost surely, 2^21317644 is an apocalyptic number.

It is an amenable number.

21317644 is a deficient number, since it is larger than the sum of its proper divisors (16656040).

21317644 is a wasteful number, since it uses less digits than its factorization.

21317644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1653 (or 1592 counting only the distinct ones).

The product of its digits is 4032, while the sum is 28.

The square root of 21317644 is about 4617.1034209773. The cubic root of 21317644 is about 277.2765032151.

Adding to 21317644 its reverse (44671312), we get a palindrome (65988956).

The spelling of 21317644 in words is "twenty-one million, three hundred seventeen thousand, six hundred forty-four".