161711581 has 2 divisors, whose sum is σ = 161711582. Its totient is φ = 161711580.

The previous prime is 161711521. The next prime is 161711591. The reversal of 161711581 is 185117161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 92256025 + 69455556 = 9605^2 + 8334^2 .

It is a cyclic number.

It is not a de Polignac number, because 161711581 - 2¹¹ = 161709533 is a prime.

It is a super-2 number, since 2×161711581² = 52301270859039122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161711521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80855790 + 80855791.

It is an arithmetic number, because the mean of its divisors is an integer number (80855791).

Almost surely, 2^161711581 is an apocalyptic number.

It is an amenable number.

161711581 is a deficient number, since it is larger than the sum of its proper divisors (1).

161711581 is an equidigital number, since it uses as much as digits as its factorization.

161711581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 31.

The square root of 161711581 is about 12716.5868455337. The cubic root of 161711581 is about 544.8124720242.

The spelling of 161711581 in words is "one hundred sixty-one million, seven hundred eleven thousand, five hundred eighty-one".