640636 has 6 divisors (see below), whose sum is σ = 1121120. Its totient is φ = 320316.

The previous prime is 640631. The next prime is 640649. The reversal of 640636 is 636046.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 640636.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80076 + ... + 80083.

2⁶⁴⁰⁶³⁶ is an apocalyptic number.

It is an amenable number.

640636 is a deficient number, since it is larger than the sum of its proper divisors (480484).

640636 is a wasteful number, since it uses less digits than its factorization.

640636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160163 (or 160161 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 640636 is about 800.3974012951. The cubic root of 640636 is about 86.2059244102.

The spelling of 640636 in words is "six hundred forty thousand, six hundred thirty-six".