639908338 has 4 divisors (see below), whose sum is σ = 959862510. Its totient is φ = 319954168.

The previous prime is 639908333. The next prime is 639908359. The reversal of 639908338 is 833809936.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 367757329 + 272151009 = 19177^2 + 16497^2 .

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 639908291 and 639908300.

It is not an unprimeable number, because it can be changed into a prime (639908333) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159977083 + ... + 159977086.

Almost surely, 2^639908338 is an apocalyptic number.

639908338 is a deficient number, since it is larger than the sum of its proper divisors (319954172).

639908338 is a wasteful number, since it uses less digits than its factorization.

639908338 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319954171.

The product of its (nonzero) digits is 839808, while the sum is 49.

The square root of 639908338 is about 25296.4095871331. The cubic root of 639908338 is about 861.7327324250.

The spelling of 639908338 in words is "six hundred thirty-nine million, nine hundred eight thousand, three hundred thirty-eight".