81517841 has 2 divisors, whose sum is σ = 81517842. Its totient is φ = 81517840.

The previous prime is 81517831. The next prime is 81517901. The reversal of 81517841 is 14871518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75777025 + 5740816 = 8705^2 + 2396^2 .

It is a cyclic number.

It is not a de Polignac number, because 81517841 - 2¹⁰ = 81516817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81517831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40758920 + 40758921.

It is an arithmetic number, because the mean of its divisors is an integer number (40758921).

Almost surely, 2^81517841 is an apocalyptic number.

It is an amenable number.

81517841 is a deficient number, since it is larger than the sum of its proper divisors (1).

81517841 is an equidigital number, since it uses as much as digits as its factorization.

81517841 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8960, while the sum is 35.

The square root of 81517841 is about 9028.7231101635. The cubic root of 81517841 is about 433.5949575292.

The spelling of 81517841 in words is "eighty-one million, five hundred seventeen thousand, eight hundred forty-one".