161051981 has 2 divisors, whose sum is σ = 161051982. Its totient is φ = 161051980.

The previous prime is 161051953. The next prime is 161052011. The reversal of 161051981 is 189150161.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 129185956 + 31866025 = 11366^2 + 5645^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161051981 is a prime.

It is a super-2 number, since 2×161051981² = 51875481168048722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161051381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80525990 + 80525991.

It is an arithmetic number, because the mean of its divisors is an integer number (80525991).

Almost surely, 2^161051981 is an apocalyptic number.

It is an amenable number.

161051981 is a deficient number, since it is larger than the sum of its proper divisors (1).

161051981 is an equidigital number, since it uses as much as digits as its factorization.

161051981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2160, while the sum is 32.

The square root of 161051981 is about 12690.6257134942. The cubic root of 161051981 is about 544.0707234410.

The spelling of 161051981 in words is "one hundred sixty-one million, fifty-one thousand, nine hundred eighty-one".