639736 has 8 divisors (see below), whose sum is σ = 1199520. Its totient is φ = 319864.

The previous prime is 639731. The next prime is 639739. The reversal of 639736 is 637936.

639736 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (8).

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 (639731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39976 + ... + 39991.

It is an arithmetic number, because the mean of its divisors is an integer number (149940).

2⁶³⁹⁷³⁶ is an apocalyptic number.

It is an amenable number.

639736 is a deficient number, since it is larger than the sum of its proper divisors (559784).

639736 is a wasteful number, since it uses less digits than its factorization.

639736 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79973 (or 79969 counting only the distinct ones).

The product of its digits is 20412, while the sum is 34.

The square root of 639736 is about 799.8349829809. The cubic root of 639736 is about 86.1655365808.

The spelling of 639736 in words is "six hundred thirty-nine thousand, seven hundred thirty-six".