639861973 has 8 divisors (see below), whose sum is σ = 655083968. Its totient is φ = 624655584.

The previous prime is 639861947. The next prime is 639861977. The reversal of 639861973 is 379168936.

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-639861973 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639861973.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639861977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 146761 + ... + 151057.

It is an arithmetic number, because the mean of its divisors is an integer number (81885496).

Almost surely, 2^639861973 is an apocalyptic number.

It is an amenable number.

639861973 is a deficient number, since it is larger than the sum of its proper divisors (15221995).

639861973 is a wasteful number, since it uses less digits than its factorization.

639861973 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7803.

The product of its digits is 1469664, while the sum is 52.

The square root of 639861973 is about 25295.4931361300. The cubic root of 639861973 is about 861.7119194425.

The spelling of 639861973 in words is "six hundred thirty-nine million, eight hundred sixty-one thousand, nine hundred seventy-three".