81305729 has 2 divisors, whose sum is σ = 81305730. Its totient is φ = 81305728.

The previous prime is 81305701. The next prime is 81305737. The reversal of 81305729 is 92750318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 50481025 + 30824704 = 7105^2 + 5552^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81305729 is a prime.

It is a super-2 number, since 2×81305729² = 13221243136442882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81305789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40652864 + 40652865.

It is an arithmetic number, because the mean of its divisors is an integer number (40652865).

Almost surely, 2^81305729 is an apocalyptic number.

It is an amenable number.

81305729 is a deficient number, since it is larger than the sum of its proper divisors (1).

81305729 is an equidigital number, since it uses as much as digits as its factorization.

81305729 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 81305729 is about 9016.9689474901. The cubic root of 81305729 is about 433.2185549396.

The spelling of 81305729 in words is "eighty-one million, three hundred five thousand, seven hundred twenty-nine".