79321866581 has 2 divisors, whose sum is σ = 79321866582. Its totient is φ = 79321866580.

The previous prime is 79321866563. The next prime is 79321866643. The reversal of 79321866581 is 18566812397.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70360215025 + 8961651556 = 265255^2 + 94666^2 .

It is a cyclic number.

It is not a de Polignac number, because 79321866581 - 2¹⁴ = 79321850197 is a prime.

It is a super-2 number, since 2×79321866581² (a number of 23 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (79321866521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39660933290 + 39660933291.

It is an arithmetic number, because the mean of its divisors is an integer number (39660933291).

Almost surely, 2^79321866581 is an apocalyptic number.

It is an amenable number.

79321866581 is a deficient number, since it is larger than the sum of its proper divisors (1).

79321866581 is an equidigital number, since it uses as much as digits as its factorization.

79321866581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4354560, while the sum is 56.

The spelling of 79321866581 in words is "seventy-nine billion, three hundred twenty-one million, eight hundred sixty-six thousand, five hundred eighty-one".