81584681 has 2 divisors, whose sum is σ = 81584682. Its totient is φ = 81584680.

The previous prime is 81584641. The next prime is 81584693. The reversal of 81584681 is 18648518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79210000 + 2374681 = 8900^2 + 1541^2 .

It is a cyclic number.

It is not a de Polignac number, because 81584681 - 2⁶ = 81584617 is a prime.

It is a super-2 number, since 2×81584681² = 13312120347743522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81584641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40792340 + 40792341.

It is an arithmetic number, because the mean of its divisors is an integer number (40792341).

Almost surely, 2^81584681 is an apocalyptic number.

It is an amenable number.

81584681 is a deficient number, since it is larger than the sum of its proper divisors (1).

81584681 is an equidigital number, since it uses as much as digits as its factorization.

81584681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 61440, while the sum is 41.

The square root of 81584681 is about 9032.4238718076. The cubic root of 81584681 is about 433.7134329008.

The spelling of 81584681 in words is "eighty-one million, five hundred eighty-four thousand, six hundred eighty-one".