639860647 has 4 divisors (see below), whose sum is σ = 657154216. Its totient is φ = 622567080.

The previous prime is 639860633. The next prime is 639860657. The reversal of 639860647 is 746068936.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639860647 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 639860647.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639860657) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8646729 + ... + 8646802.

It is an arithmetic number, because the mean of its divisors is an integer number (164288554).

Almost surely, 2^639860647 is an apocalyptic number.

639860647 is a deficient number, since it is larger than the sum of its proper divisors (17293569).

639860647 is a wasteful number, since it uses less digits than its factorization.

639860647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17293568.

The product of its (nonzero) digits is 1306368, while the sum is 49.

The square root of 639860647 is about 25295.4669259138. The cubic root of 639860647 is about 861.7113241939.

The spelling of 639860647 in words is "six hundred thirty-nine million, eight hundred sixty thousand, six hundred forty-seven".