81663555177 has 12 divisors (see below), whose sum is σ = 119002350324. Its totient is φ = 53960578560.

The previous prime is 81663555167. The next prime is 81663555179. The reversal of 81663555177 is 77155536618.

It is a happy number.

81663555177 is a `hidden beast` number, since 8 + 16 + 6 + 3 + 5 + 551 + 77 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 29743831296 + 51919723881 = 172464^2 + 227859^2 .

It is not a de Polignac number, because 81663555177 - 2¹⁶ = 81663489641 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81663555179) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 40148224 + ... + 40150257.

It is an arithmetic number, because the mean of its divisors is an integer number (9916862527).

Almost surely, 2^81663555177 is an apocalyptic number.

It is an amenable number.

81663555177 is a deficient number, since it is larger than the sum of its proper divisors (37338795147).

81663555177 is a wasteful number, since it uses less digits than its factorization.

81663555177 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80298600 (or 80298597 counting only the distinct ones).

The product of its digits is 5292000, while the sum is 54.

The spelling of 81663555177 in words is "eighty-one billion, six hundred sixty-three million, five hundred fifty-five thousand, one hundred seventy-seven".