18561564 has 72 divisors (see below), whose sum is σ = 54410720. Its totient is φ = 5225472.

The previous prime is 18561559. The next prime is 18561583. The reversal of 18561564 is 46516581.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 17892 + ... + 18900.

Almost surely, 2^18561564 is an apocalyptic number.

18561564 is a gapful number since it is divisible by the number (14) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18561564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27205360).

18561564 is an abundant number, since it is smaller than the sum of its proper divisors (35849156).

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

18561564 is a wasteful number, since it uses less digits than its factorization.

18561564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1099 (or 1094 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

The square root of 18561564 is about 4308.3133590768. The cubic root of 18561564 is about 264.7716746961.

The spelling of 18561564 in words is "eighteen million, five hundred sixty-one thousand, five hundred sixty-four".