636561 has 6 divisors (see below), whose sum is σ = 919490. Its totient is φ = 424368.

The previous prime is 636553. The next prime is 636563. The reversal of 636561 is 165636.

636561 is a `hidden beast` number, since 6 + 3 + 656 + 1 = 666.

636561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 571536 + 65025 = 756^2 + 255^2 .

It is not a de Polignac number, because 636561 - 2³ = 636553 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (636563) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35356 + ... + 35373.

2⁶³⁶⁵⁶¹ is an apocalyptic number.

It is an amenable number.

636561 is a deficient number, since it is larger than the sum of its proper divisors (282929).

636561 is a wasteful number, since it uses less digits than its factorization.

636561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70735 (or 70732 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 636561 is about 797.8477298332. The cubic root of 636561 is about 86.0227540296.

The spelling of 636561 in words is "six hundred thirty-six thousand, five hundred sixty-one".