639890 has 16 divisors (see below), whose sum is σ = 1171800. Its totient is φ = 251520.

The previous prime is 639857. The next prime is 639907. The reversal of 639890 is 98936.

It can be written as a sum of positive squares in 4 ways, for example, as 477481 + 162409 = 691^2 + 403^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 639890.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86 + ... + 1134.

2⁶³⁹⁸⁹⁰ is an apocalyptic number.

639890 is a deficient number, since it is larger than the sum of its proper divisors (531910).

639890 is a wasteful number, since it uses less digits than its factorization.

639890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1117.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 639890 is about 799.9312470456. The cubic root of 639890 is about 86.1724500722.

The spelling of 639890 in words is "six hundred thirty-nine thousand, eight hundred ninety".