639949761 has 24 divisors (see below), whose sum is σ = 1042102880. Its totient is φ = 387846360.

The previous prime is 639949729. The next prime is 639949777. The reversal of 639949761 is 167949936.

639949761 is a `hidden beast` number, since 6 + 3 + 99 + 497 + 61 = 666.

It is not a de Polignac number, because 639949761 - 2⁵ = 639949729 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 639949698 and 639949707.

It is not an unprimeable number, because it can be changed into a prime (639949561) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 94675 + ... + 101208.

Almost surely, 2^639949761 is an apocalyptic number.

It is an amenable number.

639949761 is a deficient number, since it is larger than the sum of its proper divisors (402153119).

639949761 is a wasteful number, since it uses less digits than its factorization.

639949761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195914 (or 195897 counting only the distinct ones).

The product of its digits is 2204496, while the sum is 54.

The square root of 639949761 is about 25297.2283264392. The cubic root of 639949761 is about 861.7513261218.

The spelling of 639949761 in words is "six hundred thirty-nine million, nine hundred forty-nine thousand, seven hundred sixty-one".