639557 has 6 divisors (see below), whose sum is σ = 679698. Its totient is φ = 601664.

The previous prime is 639547. The next prime is 639563. The reversal of 639557 is 755936.

It can be written as a sum of positive squares in 3 ways, for example, as 474721 + 164836 = 689^2 + 406^2 .

It is not a de Polignac number, because 639557 - 2⁶ = 639493 is a prime.

It is a d-powerful number, because it can be written as 6⁶ + 3¹² + 5 + 9⁵ + 5 + 7⁴ .

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639517) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 818 + ... + 1395.

It is an arithmetic number, because the mean of its divisors is an integer number (113283).

2⁶³⁹⁵⁵⁷ is an apocalyptic number.

It is an amenable number.

639557 is a deficient number, since it is larger than the sum of its proper divisors (40141).

639557 is a wasteful number, since it uses less digits than its factorization.

639557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2247 (or 2230 counting only the distinct ones).

The product of its digits is 28350, while the sum is 35.

The square root of 639557 is about 799.7230770711. The cubic root of 639557 is about 86.1574993749.

The spelling of 639557 in words is "six hundred thirty-nine thousand, five hundred fifty-seven".