81159509 has 2 divisors, whose sum is σ = 81159510. Its totient is φ = 81159508.

The previous prime is 81159497. The next prime is 81159517. The reversal of 81159509 is 90595118.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80604484 + 555025 = 8978^2 + 745^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81159509 is a prime.

It is a super-2 number, since 2×81159509² = 13173731802242162, 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 (81159539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40579754 + 40579755.

It is an arithmetic number, because the mean of its divisors is an integer number (40579755).

Almost surely, 2^81159509 is an apocalyptic number.

It is an amenable number.

81159509 is a deficient number, since it is larger than the sum of its proper divisors (1).

81159509 is an equidigital number, since it uses as much as digits as its factorization.

81159509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16200, while the sum is 38.

The square root of 81159509 is about 9008.8572527263. The cubic root of 81159509 is about 432.9586994158.

The spelling of 81159509 in words is "eighty-one million, one hundred fifty-nine thousand, five hundred nine".