81305789 has 2 divisors, whose sum is σ = 81305790. Its totient is φ = 81305788.

The previous prime is 81305771. The next prime is 81305797. The reversal of 81305789 is 98750318.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 43692100 + 37613689 = 6610^2 + 6133^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81305789 is a prime.

It is a super-2 number, since 2×81305789² = 13221262649825042, 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 (81305729) 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, 40652894 + 40652895.

It is an arithmetic number, because the mean of its divisors is an integer number (40652895).

Almost surely, 2^81305789 is an apocalyptic number.

It is an amenable number.

81305789 is a deficient number, since it is larger than the sum of its proper divisors (1).

81305789 is an equidigital number, since it uses as much as digits as its factorization.

81305789 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60480, while the sum is 41.

The square root of 81305789 is about 9016.9722745498. The cubic root of 81305789 is about 433.2186615048.

The spelling of 81305789 in words is "eighty-one million, three hundred five thousand, seven hundred eighty-nine".