638391011 has 4 divisors (see below), whose sum is σ = 640075800. Its totient is φ = 636706224.

The previous prime is 638390993. The next prime is 638391023. The reversal of 638391011 is 110193836.

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

It is a cyclic number.

It is not a de Polignac number, because 638391011 - 2²² = 634196707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638391071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 841826 + ... + 842583.

It is an arithmetic number, because the mean of its divisors is an integer number (160018950).

Almost surely, 2^638391011 is an apocalyptic number.

638391011 is a deficient number, since it is larger than the sum of its proper divisors (1684789).

638391011 is a wasteful number, since it uses less digits than its factorization.

638391011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1684788.

The product of its (nonzero) digits is 3888, while the sum is 32.

The square root of 638391011 is about 25266.4008319349. The cubic root of 638391011 is about 861.0510904442.

The spelling of 638391011 in words is "six hundred thirty-eight million, three hundred ninety-one thousand, eleven".