639977 has 8 divisors (see below), whose sum is σ = 725760. Its totient is φ = 559440.

The previous prime is 639959. The next prime is 639983. The reversal of 639977 is 779936.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639977 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639977.

It is not an unprimeable number, because it can be changed into a prime (639907) 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 7 ways as a sum of consecutive naturals, for example, 1049 + ... + 1542.

It is an arithmetic number, because the mean of its divisors is an integer number (90720).

2⁶³⁹⁹⁷⁷ is an apocalyptic number.

It is an amenable number.

639977 is a deficient number, since it is larger than the sum of its proper divisors (85783).

639977 is a wasteful number, since it uses less digits than its factorization.

639977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2623.

The product of its digits is 71442, while the sum is 41.

The square root of 639977 is about 799.9856248708. The cubic root of 639977 is about 86.1763552556.

Subtracting from 639977 its sum of digits (41), we obtain a palindrome (639936).

The spelling of 639977 in words is "six hundred thirty-nine thousand, nine hundred seventy-seven".