639889 has 4 divisors (see below), whose sum is σ = 641520. Its totient is φ = 638260.

The previous prime is 639857. The next prime is 639907. The reversal of 639889 is 988936.

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 not a de Polignac number, because 639889 - 2⁵ = 639857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639839) 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, 174 + ... + 1144.

It is an arithmetic number, because the mean of its divisors is an integer number (160380).

2⁶³⁹⁸⁸⁹ is an apocalyptic number.

It is an amenable number.

639889 is a deficient number, since it is larger than the sum of its proper divisors (1631).

639889 is an equidigital number, since it uses as much as digits as its factorization.

639889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1630.

The product of its digits is 93312, while the sum is 43.

The square root of 639889 is about 799.9306219917. The cubic root of 639889 is about 86.1724051830.

The spelling of 639889 in words is "six hundred thirty-nine thousand, eight hundred eighty-nine".