21559664 has 20 divisors (see below), whose sum is σ = 47739504. Its totient is φ = 9239808.

The previous prime is 21559649. The next prime is 21559667. The reversal of 21559664 is 46695512.

It is a super-2 number, since 2×21559664² = 929638223585792, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21559667) 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, 96137 + ... + 96360.

Almost surely, 2^21559664 is an apocalyptic number.

It is an amenable number.

21559664 is an abundant number, since it is smaller than the sum of its proper divisors (26179840).

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

21559664 is a wasteful number, since it uses less digits than its factorization.

21559664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192512 (or 192506 counting only the distinct ones).

The product of its digits is 64800, while the sum is 38.

The square root of 21559664 is about 4643.2385249952. The cubic root of 21559664 is about 278.3218672493.

The spelling of 21559664 in words is "twenty-one million, five hundred fifty-nine thousand, six hundred sixty-four".