639424 has 28 divisors (see below), whose sum is σ = 1294384. Its totient is φ = 313344.

The previous prime is 639391. The next prime is 639433. The reversal of 639424 is 424936.

It is a junction number, because it is equal to n+sod(n) for n = 639392 and 639401.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6157 + ... + 6259.

It is an arithmetic number, because the mean of its divisors is an integer number (46228).

2⁶³⁹⁴²⁴ is an apocalyptic number.

639424 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 639424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (647192).

639424 is an abundant number, since it is smaller than the sum of its proper divisors (654960).

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

639424 is a wasteful number, since it uses less digits than its factorization.

639424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212 (or 202 counting only the distinct ones).

The product of its digits is 5184, while the sum is 28.

The square root of 639424 is about 799.6399189635. The cubic root of 639424 is about 86.1515266251.

The spelling of 639424 in words is "six hundred thirty-nine thousand, four hundred twenty-four".