639724306809 has 32 divisors (see below), whose sum is σ = 1032401258496. Its totient is φ = 343973064960.

The previous prime is 639724306801. The next prime is 639724306817. The reversal of 639724306809 is 908603427936.

It is an interprime number because it is at equal distance from previous prime (639724306801) and next prime (639724306817).

It is not a de Polignac number, because 639724306809 - 2³ = 639724306801 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639724306801) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1337674 + ... + 1751804.

It is an arithmetic number, because the mean of its divisors is an integer number (32262539328).

Almost surely, 2^639724306809 is an apocalyptic number.

It is an amenable number.

639724306809 is a deficient number, since it is larger than the sum of its proper divisors (392676951687).

639724306809 is a wasteful number, since it uses less digits than its factorization.

639724306809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 418485.

The product of its (nonzero) digits is 11757312, while the sum is 57.

The spelling of 639724306809 in words is "six hundred thirty-nine billion, seven hundred twenty-four million, three hundred six thousand, eight hundred nine".