81985177 has 2 divisors, whose sum is σ = 81985178. Its totient is φ = 81985176.

The previous prime is 81985151. The next prime is 81985181. The reversal of 81985177 is 77158918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72182016 + 9803161 = 8496^2 + 3131^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81985177 is a prime.

It is equal to p_4778587 and since 81985177 and 4778587 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81985147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40992588 + 40992589.

It is an arithmetic number, because the mean of its divisors is an integer number (40992589).

Almost surely, 2^81985177 is an apocalyptic number.

It is an amenable number.

81985177 is a deficient number, since it is larger than the sum of its proper divisors (1).

81985177 is an equidigital number, since it uses as much as digits as its factorization.

81985177 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 46.

The square root of 81985177 is about 9054.5666378905. The cubic root of 81985177 is about 434.4219688493.

The spelling of 81985177 in words is "eighty-one million, nine hundred eighty-five thousand, one hundred seventy-seven".