638816161 has 4 divisors (see below), whose sum is σ = 639393300. Its totient is φ = 638239024.

The previous prime is 638816153. The next prime is 638816207. The reversal of 638816161 is 161618836.

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 5035536 + 633780625 = 2244^2 + 25175^2 .

It is a cyclic number.

It is not a de Polignac number, because 638816161 - 2³ = 638816153 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638816111) 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, 286906 + ... + 289123.

It is an arithmetic number, because the mean of its divisors is an integer number (159848325).

Almost surely, 2^638816161 is an apocalyptic number.

It is an amenable number.

638816161 is a deficient number, since it is larger than the sum of its proper divisors (577139).

638816161 is a wasteful number, since it uses less digits than its factorization.

638816161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 577138.

The product of its digits is 41472, while the sum is 40.

The square root of 638816161 is about 25274.8127787329. The cubic root of 638816161 is about 861.2421930911.

The spelling of 638816161 in words is "six hundred thirty-eight million, eight hundred sixteen thousand, one hundred sixty-one".