181161661 has 2 divisors, whose sum is σ = 181161662. Its totient is φ = 181161660.

The previous prime is 181161649. The next prime is 181161667. The reversal of 181161661 is 166161181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 142348761 + 38812900 = 11931^2 + 6230^2 .

It is a cyclic number.

It is not a de Polignac number, because 181161661 - 2¹¹ = 181159613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (181161667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90580830 + 90580831.

It is an arithmetic number, because the mean of its divisors is an integer number (90580831).

Almost surely, 2^181161661 is an apocalyptic number.

It is an amenable number.

181161661 is a deficient number, since it is larger than the sum of its proper divisors (1).

181161661 is an equidigital number, since it uses as much as digits as its factorization.

181161661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 31.

The square root of 181161661 is about 13459.6307898842. The cubic root of 181161661 is about 565.8336413366.

The spelling of 181161661 in words is "one hundred eighty-one million, one hundred sixty-one thousand, six hundred sixty-one".