81966161 has 2 divisors, whose sum is σ = 81966162. Its totient is φ = 81966160.

The previous prime is 81966121. The next prime is 81966169. The reversal of 81966161 is 16166918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81793936 + 172225 = 9044^2 + 415^2 .

It is a cyclic number.

It is not a de Polignac number, because 81966161 - 2⁶ = 81966097 is a prime.

It is not a weakly prime, because it can be changed into another prime (81966169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40983080 + 40983081.

It is an arithmetic number, because the mean of its divisors is an integer number (40983081).

Almost surely, 2^81966161 is an apocalyptic number.

It is an amenable number.

81966161 is a deficient number, since it is larger than the sum of its proper divisors (1).

81966161 is an equidigital number, since it uses as much as digits as its factorization.

81966161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15552, while the sum is 38.

The square root of 81966161 is about 9053.5164991289. The cubic root of 81966161 is about 434.3883790093.

The spelling of 81966161 in words is "eighty-one million, nine hundred sixty-six thousand, one hundred sixty-one".