639725 has 6 divisors (see below), whose sum is σ = 793290. Its totient is φ = 511760.

The previous prime is 639719. The next prime is 639731. The reversal of 639725 is 527936.

It is an interprime number because it is at equal distance from previous prime (639719) and next prime (639731).

It can be written as a sum of positive squares in 3 ways, for example, as 139876 + 499849 = 374^2 + 707^2 .

It is not a de Polignac number, because 639725 - 2¹⁴ = 623341 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 639691 and 639700.

It is a congruent number.

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 12770 + ... + 12819.

It is an arithmetic number, because the mean of its divisors is an integer number (132215).

2⁶³⁹⁷²⁵ is an apocalyptic number.

It is an amenable number.

639725 is a deficient number, since it is larger than the sum of its proper divisors (153565).

639725 is a wasteful number, since it uses less digits than its factorization.

639725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25599 (or 25594 counting only the distinct ones).

The product of its digits is 11340, while the sum is 32.

The square root of 639725 is about 799.8281065329. The cubic root of 639725 is about 86.1650427175.

The spelling of 639725 in words is "six hundred thirty-nine thousand, seven hundred twenty-five".