639744 has 108 divisors (see below), whose sum is σ = 2097144. Its totient is φ = 172032.

The previous prime is 639739. The next prime is 639757. The reversal of 639744 is 447936.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 37624 + ... + 37640.

It is an arithmetic number, because the mean of its divisors is an integer number (19418).

2⁶³⁹⁷⁴⁴ is an apocalyptic number.

639744 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1048572).

639744 is an abundant number, since it is smaller than the sum of its proper divisors (1457400).

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

639744 is a wasteful number, since it uses less digits than its factorization.

639744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50 (or 29 counting only the distinct ones).

The product of its digits is 18144, while the sum is 33.

The square root of 639744 is about 799.8399839968. The cubic root of 639744 is about 86.1658957505.

It can be divided in two parts, 6397 and 44, that added together give a triangular number (6441 = T₁₁₃).

The spelling of 639744 in words is "six hundred thirty-nine thousand, seven hundred forty-four".