639929761 has 4 divisors (see below), whose sum is σ = 639980800. Its totient is φ = 639878724.

The previous prime is 639929707. The next prime is 639929767. The reversal of 639929761 is 167929936.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639929761 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639929699 and 639929708.

It is not an unprimeable number, because it can be changed into a prime (639929767) 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, 7720 + ... + 36598.

It is an arithmetic number, because the mean of its divisors is an integer number (159995200).

Almost surely, 2^639929761 is an apocalyptic number.

It is an amenable number.

639929761 is a deficient number, since it is larger than the sum of its proper divisors (51039).

639929761 is a wasteful number, since it uses less digits than its factorization.

639929761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51038.

The product of its digits is 1102248, while the sum is 52.

The square root of 639929761 is about 25296.8330231276. The cubic root of 639929761 is about 861.7423487472.

The spelling of 639929761 in words is "six hundred thirty-nine million, nine hundred twenty-nine thousand, seven hundred sixty-one".