638818870811 has 4 divisors (see below), whose sum is σ = 696893313624. Its totient is φ = 580744428000.

The previous prime is 638818870793. The next prime is 638818870841. The reversal of 638818870811 is 118078818836.

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-638818870811 is a prime.

It is a super-2 number, since 2×638818870811² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638818870841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29037221390 + ... + 29037221411.

It is an arithmetic number, because the mean of its divisors is an integer number (174223328406).

Almost surely, 2^638818870811 is an apocalyptic number.

638818870811 is a deficient number, since it is larger than the sum of its proper divisors (58074442813).

638818870811 is a wasteful number, since it uses less digits than its factorization.

638818870811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58074442812.

The product of its (nonzero) digits is 4128768, while the sum is 59.

The spelling of 638818870811 in words is "six hundred thirty-eight billion, eight hundred eighteen million, eight hundred seventy thousand, eight hundred eleven".