639918 has 24 divisors (see below), whose sum is σ = 1408368. Its totient is φ = 209952.

The previous prime is 639911. The next prime is 639937. The reversal of 639918 is 819936.

639918 is a `hidden beast` number, since 639 + 9 + 18 = 666.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639918.

It is not an unprimeable number, because it can be changed into a prime (639911) 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 in 11 ways as a sum of consecutive naturals, for example, 1071 + ... + 1557.

It is an arithmetic number, because the mean of its divisors is an integer number (58682).

2⁶³⁹⁹¹⁸ is an apocalyptic number.

639918 is an abundant number, since it is smaller than the sum of its proper divisors (768450).

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

639918 is a wasteful number, since it uses less digits than its factorization.

639918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 568 (or 565 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 639918 is about 799.9487483583. The cubic root of 639918 is about 86.1737069515.

The spelling of 639918 in words is "six hundred thirty-nine thousand, nine hundred eighteen".