191165981 has 2 divisors, whose sum is σ = 191165982. Its totient is φ = 191165980.

The previous prime is 191165977. The next prime is 191166023. The reversal of 191165981 is 189561191.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 180499225 + 10666756 = 13435^2 + 3266^2 .

It is an emirp because it is prime and its reverse (189561191) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 191165981 - 2² = 191165977 is a prime.

It is a super-2 number, since 2×191165981² = 73088864583384722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191165281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95582990 + 95582991.

It is an arithmetic number, because the mean of its divisors is an integer number (95582991).

Almost surely, 2^191165981 is an apocalyptic number.

It is an amenable number.

191165981 is a deficient number, since it is larger than the sum of its proper divisors (1).

191165981 is an equidigital number, since it uses as much as digits as its factorization.

191165981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19440, while the sum is 41.

The square root of 191165981 is about 13826.2786388818. The cubic root of 191165981 is about 576.0632937858.

The spelling of 191165981 in words is "one hundred ninety-one million, one hundred sixty-five thousand, nine hundred eighty-one".