639738 has 40 divisors (see below), whose sum is σ = 1568160. Its totient is φ = 193320.

The previous prime is 639731. The next prime is 639739. The reversal of 639738 is 837936.

It is a nialpdrome in base 15.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639738.

It is not an unprimeable number, because it can be changed into a prime (639731) by changing a digit.

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 19 ways as a sum of consecutive naturals, for example, 1603 + ... + 1961.

It is an arithmetic number, because the mean of its divisors is an integer number (39204).

2⁶³⁹⁷³⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639738, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (784080).

639738 is an abundant number, since it is smaller than the sum of its proper divisors (928422).

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

639738 is a wasteful number, since it uses less digits than its factorization.

639738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 384 (or 375 counting only the distinct ones).

The product of its digits is 27216, while the sum is 36.

The square root of 639738 is about 799.8362332378. The cubic root of 639738 is about 86.1656263735.

It can be divided in two parts, 63 and 9738, that added together give a square (9801 = 99²).

The spelling of 639738 in words is "six hundred thirty-nine thousand, seven hundred thirty-eight".