21481564 has 24 divisors (see below), whose sum is σ = 41046320. Its totient is φ = 9777024.

The previous prime is 21481561. The next prime is 21481567. The reversal of 21481564 is 46518412.

It is an interprime number because it is at equal distance from previous prime (21481561) and next prime (21481567).

It is a super-2 number, since 2×21481564² = 922915183772192, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 967 + ... + 6625.

Almost surely, 2^21481564 is an apocalyptic number.

It is an amenable number.

21481564 is a deficient number, since it is larger than the sum of its proper divisors (19564756).

21481564 is a wasteful number, since it uses less digits than its factorization.

21481564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5749 (or 5747 counting only the distinct ones).

The product of its digits is 7680, while the sum is 31.

The square root of 21481564 is about 4634.8208163855. The cubic root of 21481564 is about 277.9853864616.

Adding to 21481564 its reverse (46518412), we get a palindrome (67999976).

The spelling of 21481564 in words is "twenty-one million, four hundred eighty-one thousand, five hundred sixty-four".