639665889 has 4 divisors (see below), whose sum is σ = 852887856. Its totient is φ = 426443924.

The previous prime is 639665881. The next prime is 639665933. The reversal of 639665889 is 988566936.

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.

It is a cyclic number.

It is not a de Polignac number, because 639665889 - 2³ = 639665881 is a prime.

It is not an unprimeable number, because it can be changed into a prime (639665881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106610979 + ... + 106610984.

It is an arithmetic number, because the mean of its divisors is an integer number (213221964).

Almost surely, 2^639665889 is an apocalyptic number.

It is an amenable number.

639665889 is a deficient number, since it is larger than the sum of its proper divisors (213221967).

639665889 is a wasteful number, since it uses less digits than its factorization.

639665889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213221966.

The product of its digits is 16796160, while the sum is 60.

The square root of 639665889 is about 25291.6169708463. The cubic root of 639665889 is about 861.6238873408.

The spelling of 639665889 in words is "six hundred thirty-nine million, six hundred sixty-five thousand, eight hundred eighty-nine".