639761 has 4 divisors (see below), whose sum is σ = 677412. Its totient is φ = 602112.

The previous prime is 639757. The next prime is 639833. The reversal of 639761 is 167936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 330625 + 309136 = 575^2 + 556^2 .

It is a cyclic number.

It is not a de Polignac number, because 639761 - 2² = 639757 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639701) 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, 18800 + ... + 18833.

It is an arithmetic number, because the mean of its divisors is an integer number (169353).

2⁶³⁹⁷⁶¹ is an apocalyptic number.

It is an amenable number.

639761 is a deficient number, since it is larger than the sum of its proper divisors (37651).

639761 is a wasteful number, since it uses less digits than its factorization.

639761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37650.

The product of its digits is 6804, while the sum is 32.

The square root of 639761 is about 799.8506110518. The cubic root of 639761 is about 86.1666589763.

The spelling of 639761 in words is "six hundred thirty-nine thousand, seven hundred sixty-one".