636681 has 4 divisors (see below), whose sum is σ = 848912. Its totient is φ = 424452.

The previous prime is 636673. The next prime is 636697. The reversal of 636681 is 186636.

636681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 not a de Polignac number, because 636681 - 2³ = 636673 is a prime.

It is a super-2 number, since 2×636681² = 810725391522, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

636681 is a lucky number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 636681.

It is not an unprimeable number, because it can be changed into a prime (636631) 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, 106111 + ... + 106116.

It is an arithmetic number, because the mean of its divisors is an integer number (212228).

2⁶³⁶⁶⁸¹ is an apocalyptic number.

It is an amenable number.

636681 is a deficient number, since it is larger than the sum of its proper divisors (212231).

636681 is a wasteful number, since it uses less digits than its factorization.

636681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212230.

The product of its digits is 5184, while the sum is 30.

The square root of 636681 is about 797.9229286090. The cubic root of 636681 is about 86.0281591581.

It can be divided in two parts, 63 and 6681, that multiplied together give a triangular number (420903 = T₉₁₇).

The spelling of 636681 in words is "six hundred thirty-six thousand, six hundred eighty-one".