55991565 has 72 divisors (see below), whose sum is σ = 114884640. Its totient is φ = 25147584.

The previous prime is 55991561. The next prime is 55991567. The reversal of 55991565 is 56519955.

55991565 is a `hidden beast` number, since 5 + 599 + 1 + 56 + 5 = 666.

It is not a de Polignac number, because 55991565 - 2² = 55991561 is a prime.

It is a super-2 number, since 2×55991565² = 6270110702298450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 55991565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55991561) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 147546 + ... + 147924.

It is an arithmetic number, because the mean of its divisors is an integer number (1595620).

Almost surely, 2^55991565 is an apocalyptic number.

It is an amenable number.

55991565 is an abundant number, since it is smaller than the sum of its proper divisors (58893075).

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

55991565 is a wasteful number, since it uses less digits than its factorization.

55991565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 471 (or 461 counting only the distinct ones).

The product of its digits is 303750, while the sum is 45.

The square root of 55991565 is about 7482.7511651798. The cubic root of 55991565 is about 382.5670265727.

The spelling of 55991565 in words is "fifty-five million, nine hundred ninety-one thousand, five hundred sixty-five".