636116561 has 4 divisors (see below), whose sum is σ = 669596400. Its totient is φ = 602636724.

The previous prime is 636116531. The next prime is 636116563. The reversal of 636116561 is 165611636.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-636116561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (636116563) 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, 16739891 + ... + 16739928.

It is an arithmetic number, because the mean of its divisors is an integer number (167399100).

Almost surely, 2^636116561 is an apocalyptic number.

It is an amenable number.

636116561 is a deficient number, since it is larger than the sum of its proper divisors (33479839).

636116561 is a wasteful number, since it uses less digits than its factorization.

636116561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33479838.

The product of its digits is 19440, while the sum is 35.

The square root of 636116561 is about 25221.3512921096. The cubic root of 636116561 is about 860.0272936173.

It can be divided in two parts, 6361 and 16561, that added together give a palindrome (22922).

The spelling of 636116561 in words is "six hundred thirty-six million, one hundred sixteen thousand, five hundred sixty-one".