639698 has 4 divisors (see below), whose sum is σ = 959550. Its totient is φ = 319848.

The previous prime is 639697. The next prime is 639701. The reversal of 639698 is 896936.

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., 635209 + 4489 = 797^2 + 67^2 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639698.

It is not an unprimeable number, because it can be changed into a prime (639697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159923 + ... + 159926.

2⁶³⁹⁶⁹⁸ is an apocalyptic number.

639698 is a deficient number, since it is larger than the sum of its proper divisors (319852).

639698 is a wasteful number, since it uses less digits than its factorization.

639698 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319851.

The product of its digits is 69984, while the sum is 41.

The square root of 639698 is about 799.8112277281. The cubic root of 639698 is about 86.1638304837.

The spelling of 639698 in words is "six hundred thirty-nine thousand, six hundred ninety-eight".