81807793 has 2 divisors, whose sum is σ = 81807794. Its totient is φ = 81807792.

The previous prime is 81807767. The next prime is 81807799. The reversal of 81807793 is 39770818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63728289 + 18079504 = 7983^2 + 4252^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81807793 is a prime.

It is not a weakly prime, because it can be changed into another prime (81807799) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40903896 + 40903897.

It is an arithmetic number, because the mean of its divisors is an integer number (40903897).

Almost surely, 2^81807793 is an apocalyptic number.

It is an amenable number.

81807793 is a deficient number, since it is larger than the sum of its proper divisors (1).

81807793 is an equidigital number, since it uses as much as digits as its factorization.

81807793 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84672, while the sum is 43.

The square root of 81807793 is about 9044.7660555705. The cubic root of 81807793 is about 434.1084359570.

The spelling of 81807793 in words is "eighty-one million, eight hundred seven thousand, seven hundred ninety-three".