639381 has 8 divisors (see below), whose sum is σ = 865504. Its totient is φ = 419760.

The previous prime is 639371. The next prime is 639391. The reversal of 639381 is 183936.

It is an interprime number because it is at equal distance from previous prime (639371) and next prime (639391).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 639381 - 2⁷ = 639253 is a prime.

It is a super-2 number, since 2×639381² = 817616126322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639381.

It is not an unprimeable number, because it can be changed into a prime (639311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1390 + ... + 1791.

It is an arithmetic number, because the mean of its divisors is an integer number (108188).

2⁶³⁹³⁸¹ is an apocalyptic number.

It is an amenable number.

639381 is a deficient number, since it is larger than the sum of its proper divisors (226123).

639381 is a wasteful number, since it uses less digits than its factorization.

639381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3251.

The product of its digits is 3888, while the sum is 30.

The square root of 639381 is about 799.6130314096. The cubic root of 639381 is about 86.1495954086.

The spelling of 639381 in words is "six hundred thirty-nine thousand, three hundred eighty-one".