638840742663 has 4 divisors (see below), whose sum is σ = 851787656888. Its totient is φ = 425893828440.

The previous prime is 638840742637. The next prime is 638840742691. The reversal of 638840742663 is 366247048836.

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

It is a de Polignac number, because none of the positive numbers 2^k-638840742663 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638840752663) 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, 106473457108 + ... + 106473457113.

It is an arithmetic number, because the mean of its divisors is an integer number (212946914222).

Almost surely, 2^638840742663 is an apocalyptic number.

638840742663 is a deficient number, since it is larger than the sum of its proper divisors (212946914225).

638840742663 is a wasteful number, since it uses less digits than its factorization.

638840742663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212946914224.

The product of its (nonzero) digits is 27869184, while the sum is 57.

The spelling of 638840742663 in words is "six hundred thirty-eight billion, eight hundred forty million, seven hundred forty-two thousand, six hundred sixty-three".