81313569791989 has 2 divisors, whose sum is σ = 81313569791990. Its totient is φ = 81313569791988.

The previous prime is 81313569791969. The next prime is 81313569792001. The reversal of 81313569791989 is 98919796531318.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77222792522500 + 4090777269489 = 8787650^2 + 2022567^2 .

It is a cyclic number.

It is not a de Polignac number, because 81313569791989 - 2¹⁹ = 81313569267701 is a prime.

It is a super-2 number, since 2×81313569791989² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81313569791969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40656784895994 + 40656784895995.

It is an arithmetic number, because the mean of its divisors is an integer number (40656784895995).

Almost surely, 2^{81313569791989} is an apocalyptic number.

It is an amenable number.

81313569791989 is a deficient number, since it is larger than the sum of its proper divisors (1).

81313569791989 is an equidigital number, since it uses as much as digits as its factorization.

81313569791989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 793618560, while the sum is 79.

The spelling of 81313569791989 in words is "eighty-one trillion, three hundred thirteen billion, five hundred sixty-nine million, seven hundred ninety-one thousand, nine hundred eighty-nine".