51661161555165 has 36 divisors (see below), whose sum is σ = 92985366472284. Its totient is φ = 27552619478592.

The previous prime is 51661161555149. The next prime is 51661161555187. The reversal of 51661161555165 is 56155516116615.

51661161555165 is a `hidden beast` number, since 5 + 1 + 6 + 6 + 1 + 1 + 615 + 5 + 5 + 16 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 13584104378244 + 38077057176921 = 3685662^2 + 6170661^2 .

It is not a de Polignac number, because 51661161555165 - 2⁴ = 51661161555149 is a prime.

It is a super-2 number, since 2×51661161555165² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 787364872 + ... + 787430481.

Almost surely, 2^{51661161555165} is an apocalyptic number.

It is an amenable number.

51661161555165 is a deficient number, since it is larger than the sum of its proper divisors (41324204917119).

51661161555165 is an frugal number, since it uses more digits than its factorization.

51661161555165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1574795382 (or 1574795361 counting only the distinct ones).

The product of its digits is 4050000, while the sum is 54.

The spelling of 51661161555165 in words is "fifty-one trillion, six hundred sixty-one billion, one hundred sixty-one million, five hundred fifty-five thousand, one hundred sixty-five".