815566772161 has 4 divisors (see below), whose sum is σ = 815569056900. Its totient is φ = 815564487424.

The previous prime is 815566772129. The next prime is 815566772177. The reversal of 815566772161 is 161277665518.

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 53296339600 + 762270432561 = 230860^2 + 873081^2 .

It is a cyclic number.

It is not a de Polignac number, because 815566772161 - 2⁵ = 815566772129 is a prime.

It is a super-2 number, since 2×815566772161² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (815566772191) 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, 478216 + ... + 1363753.

It is an arithmetic number, because the mean of its divisors is an integer number (203892264225).

Almost surely, 2^815566772161 is an apocalyptic number.

It is an amenable number.

815566772161 is a deficient number, since it is larger than the sum of its proper divisors (2284739).

815566772161 is a wasteful number, since it uses less digits than its factorization.

815566772161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2284738.

The product of its digits is 4233600, while the sum is 55.

The spelling of 815566772161 in words is "eight hundred fifteen billion, five hundred sixty-six million, seven hundred seventy-two thousand, one hundred sixty-one".