636639 has 8 divisors (see below), whose sum is σ = 855600. Its totient is φ = 421056.

The previous prime is 636631. The next prime is 636653. The reversal of 636639 is 936636.

636639 is digitally balanced in base 7, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 636639 - 2³ = 636631 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

636639 is strictly pandigital in base 7.

It is a plaindrome in base 8.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 364 + ... + 1185.

It is an arithmetic number, because the mean of its divisors is an integer number (106950).

2⁶³⁶⁶³⁹ is an apocalyptic number.

636639 is a deficient number, since it is larger than the sum of its proper divisors (218961).

636639 is a wasteful number, since it uses less digits than its factorization.

636639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1689.

The product of its digits is 17496, while the sum is 33.

The square root of 636639 is about 797.8966098437. The cubic root of 636639 is about 86.0262674404.

It can be divided in two parts, 636 and 639, that added together give a triangular number (1275 = T₅₀).

The spelling of 636639 in words is "six hundred thirty-six thousand, six hundred thirty-nine".