81156161 has 2 divisors, whose sum is σ = 81156162. Its totient is φ = 81156160.

The previous prime is 81156157. The next prime is 81156209. The reversal of 81156161 is 16165118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73427761 + 7728400 = 8569^2 + 2780^2 .

It is a cyclic number.

It is not a de Polignac number, because 81156161 - 2² = 81156157 is a prime.

It is not a weakly prime, because it can be changed into another prime (81156151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40578080 + 40578081.

It is an arithmetic number, because the mean of its divisors is an integer number (40578081).

Almost surely, 2^81156161 is an apocalyptic number.

It is an amenable number.

81156161 is a deficient number, since it is larger than the sum of its proper divisors (1).

81156161 is an equidigital number, since it uses as much as digits as its factorization.

81156161 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1440, while the sum is 29.

The square root of 81156161 is about 9008.6714336799. The cubic root of 81156161 is about 432.9527458491.

The spelling of 81156161 in words is "eighty-one million, one hundred fifty-six thousand, one hundred sixty-one".