639040 has 28 divisors (see below), whose sum is σ = 1522476. Its totient is φ = 255488.

The previous prime is 639011. The next prime is 639043. The reversal of 639040 is 40936.

It can be written as a sum of positive squares in 2 ways, for example, as 97344 + 541696 = 312^2 + 736^2 .

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (639043) by changing a digit.

639040 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 679 + ... + 1318.

2⁶³⁹⁰⁴⁰ is an apocalyptic number.

It is an amenable number.

639040 is an abundant number, since it is smaller than the sum of its proper divisors (883436).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639040 is a wasteful number, since it uses less digits than its factorization.

639040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2014 (or 2004 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 639040 is about 799.3997748311. The cubic root of 639040 is about 86.1342773452.

Adding to 639040 its reverse (40936), we get a palindrome (679976).

The spelling of 639040 in words is "six hundred thirty-nine thousand, forty".