639681193 has 4 divisors (see below), whose sum is σ = 642059460. Its totient is φ = 637302928.

The previous prime is 639681179. The next prime is 639681209. The reversal of 639681193 is 391186936.

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

It can be written as a sum of positive squares in 2 ways, for example, as 67371264 + 572309929 = 8208^2 + 23923^2 .

It is a cyclic number.

It is not a de Polignac number, because 639681193 - 2⁹ = 639680681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (639681143) 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 3 ways as a sum of consecutive naturals, for example, 1188730 + ... + 1189267.

It is an arithmetic number, because the mean of its divisors is an integer number (160514865).

Almost surely, 2^639681193 is an apocalyptic number.

It is an amenable number.

639681193 is a deficient number, since it is larger than the sum of its proper divisors (2378267).

639681193 is a wasteful number, since it uses less digits than its factorization.

639681193 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2378266.

The product of its digits is 209952, while the sum is 46.

The square root of 639681193 is about 25291.9195198783. The cubic root of 639681193 is about 861.6307587336.

The spelling of 639681193 in words is "six hundred thirty-nine million, six hundred eighty-one thousand, one hundred ninety-three".