638791779 has 16 divisors (see below), whose sum is σ = 902748672. Its totient is φ = 400399488.

The previous prime is 638791733. The next prime is 638791781. The reversal of 638791779 is 977197836.

It is not a de Polignac number, because 638791779 - 2⁷ = 638791651 is a prime.

It is not an unprimeable number, because it can be changed into a prime (638791379) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 48322 + ... + 60104.

It is an arithmetic number, because the mean of its divisors is an integer number (56421792).

Almost surely, 2^638791779 is an apocalyptic number.

638791779 is a deficient number, since it is larger than the sum of its proper divisors (263956893).

638791779 is a wasteful number, since it uses less digits than its factorization.

638791779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12866.

The product of its digits is 4000752, while the sum is 57.

The square root of 638791779 is about 25274.3304362351. The cubic root of 638791779 is about 861.2312358050.

The spelling of 638791779 in words is "six hundred thirty-eight million, seven hundred ninety-one thousand, seven hundred seventy-nine".