56661561 has 48 divisors (see below), whose sum is σ = 95629248. Its totient is φ = 31948800.

The previous prime is 56661559. The next prime is 56661569. The reversal of 56661561 is 16516665.

It is not a de Polignac number, because 56661561 - 2¹ = 56661559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (56661569) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 220345 + ... + 220601.

It is an arithmetic number, because the mean of its divisors is an integer number (1992276).

Almost surely, 2^56661561 is an apocalyptic number.

56661561 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

56661561 is a deficient number, since it is larger than the sum of its proper divisors (38967687).

56661561 is a wasteful number, since it uses less digits than its factorization.

56661561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 422 (or 419 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 56661561 is about 7527.3873953717. The cubic root of 56661561 is about 384.0869147337.

Subtracting from 56661561 its reverse (16516665), we obtain a square (40144896 = 6336²).

It can be divided in two parts, 5666 and 1561, that added together give a palindrome (7227).

The spelling of 56661561 in words is "fifty-six million, six hundred sixty-one thousand, five hundred sixty-one".