639740 has 24 divisors (see below), whose sum is σ = 1391040. Its totient is φ = 246848.

The previous prime is 639739. The next prime is 639757. The reversal of 639740 is 47936.

639740 = T₁₁₅ + T₁₁₆ + ... + T₁₇₄.

It is a Harshad number since it is a multiple of its sum of digits (29).

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 7 ways as a sum of consecutive naturals, for example, 29 + ... + 1131.

It is an arithmetic number, because the mean of its divisors is an integer number (57960).

2⁶³⁹⁷⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (695520).

639740 is an abundant number, since it is smaller than the sum of its proper divisors (751300).

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

639740 is a wasteful number, since it uses less digits than its factorization.

639740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1141 (or 1139 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 29.

The square root of 639740 is about 799.8374834927. The cubic root of 639740 is about 86.1657161661.

The spelling of 639740 in words is "six hundred thirty-nine thousand, seven hundred forty".