639636 has 24 divisors (see below), whose sum is σ = 1506624. Its totient is φ = 211200.

The previous prime is 639631. The next prime is 639637. The reversal of 639636 is 636936.

It is a junction number, because it is equal to n+sod(n) for n = 639597 and 639606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639631) 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, 1636 + ... + 1988.

It is an arithmetic number, because the mean of its divisors is an integer number (62776).

2⁶³⁹⁶³⁶ is an apocalyptic number.

It is an amenable number.

639636 is an abundant number, since it is smaller than the sum of its proper divisors (866988).

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

639636 is a wasteful number, since it uses less digits than its factorization.

639636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 511 (or 509 counting only the distinct ones).

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

The square root of 639636 is about 799.7724676431. The cubic root of 639636 is about 86.1610467065.

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

The spelling of 639636 in words is "six hundred thirty-nine thousand, six hundred thirty-six".