161911081 has 2 divisors, whose sum is σ = 161911082. Its totient is φ = 161911080.

The previous prime is 161911073. The next prime is 161911093. The reversal of 161911081 is 180119161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 151290000 + 10621081 = 12300^2 + 3259^2 .

It is a cyclic number.

It is not a de Polignac number, because 161911081 - 2³ = 161911073 is a prime.

It is a super-3 number, since 3×161911081³ (a number of 26 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not a weakly prime, because it can be changed into another prime (161917081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80955540 + 80955541.

It is an arithmetic number, because the mean of its divisors is an integer number (80955541).

Almost surely, 2^161911081 is an apocalyptic number.

It is an amenable number.

161911081 is a deficient number, since it is larger than the sum of its proper divisors (1).

161911081 is an equidigital number, since it uses as much as digits as its factorization.

161911081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 432, while the sum is 28.

The square root of 161911081 is about 12724.4285136897. The cubic root of 161911081 is about 545.0364209872.

The spelling of 161911081 in words is "one hundred sixty-one million, nine hundred eleven thousand, eighty-one".