638742668 has 24 divisors (see below), whose sum is σ = 1124323200. Its totient is φ = 317514368.

The previous prime is 638742659. The next prime is 638742733. The reversal of 638742668 is 866247836.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 744896 + ... + 745752.

It is an arithmetic number, because the mean of its divisors is an integer number (46846800).

Almost surely, 2^638742668 is an apocalyptic number.

It is an amenable number.

638742668 is a deficient number, since it is larger than the sum of its proper divisors (485580532).

638742668 is a wasteful number, since it uses less digits than its factorization.

638742668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1729 (or 1727 counting only the distinct ones).

The product of its digits is 2322432, while the sum is 50.

The square root of 638742668 is about 25273.3588586875. The cubic root of 638742668 is about 861.2091644444.

The spelling of 638742668 in words is "six hundred thirty-eight million, seven hundred forty-two thousand, six hundred sixty-eight".