81170591 has 2 divisors, whose sum is σ = 81170592. Its totient is φ = 81170590.

The previous prime is 81170561. The next prime is 81170599. The reversal of 81170591 is 19507118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81170591 - 2¹⁰ = 81169567 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81170599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40585295 + 40585296.

It is an arithmetic number, because the mean of its divisors is an integer number (40585296).

Almost surely, 2^81170591 is an apocalyptic number.

81170591 is a deficient number, since it is larger than the sum of its proper divisors (1).

81170591 is an equidigital number, since it uses as much as digits as its factorization.

81170591 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 32.

The square root of 81170591 is about 9009.4722930924. The cubic root of 81170591 is about 432.9784047672.

The spelling of 81170591 in words is "eighty-one million, one hundred seventy thousand, five hundred ninety-one".