638841174721 has 4 divisors (see below), whose sum is σ = 638866634452. Its totient is φ = 638815714992.

The previous prime is 638841174701. The next prime is 638841174743. The reversal of 638841174721 is 127471148836.

It is a happy number.

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 422969430321 + 215871744400 = 650361^2 + 464620^2 .

It is a cyclic number.

It is not a de Polignac number, because 638841174721 - 2¹⁷ = 638841043649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638841174701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12692190 + ... + 12742423.

It is an arithmetic number, because the mean of its divisors is an integer number (159716658613).

Almost surely, 2^638841174721 is an apocalyptic number.

It is an amenable number.

638841174721 is a deficient number, since it is larger than the sum of its proper divisors (25459731).

638841174721 is a wasteful number, since it uses less digits than its factorization.

638841174721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25459730.

The product of its digits is 1806336, while the sum is 52.

The spelling of 638841174721 in words is "six hundred thirty-eight billion, eight hundred forty-one million, one hundred seventy-four thousand, seven hundred twenty-one".