81000813749 has 2 divisors, whose sum is σ = 81000813750. Its totient is φ = 81000813748.

The previous prime is 81000813739. The next prime is 81000813763. The reversal of 81000813749 is 94731800018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 68722622500 + 12278191249 = 262150^2 + 110807^2 .

It is a cyclic number.

It is not a de Polignac number, because 81000813749 - 2⁸ = 81000813493 is a prime.

It is a super-2 number, since 2×81000813749² (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 (81000813739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40500406874 + 40500406875.

It is an arithmetic number, because the mean of its divisors is an integer number (40500406875).

Almost surely, 2^81000813749 is an apocalyptic number.

It is an amenable number.

81000813749 is a deficient number, since it is larger than the sum of its proper divisors (1).

81000813749 is an equidigital number, since it uses as much as digits as its factorization.

81000813749 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48384, while the sum is 41.

The spelling of 81000813749 in words is "eighty-one billion, eight hundred thirteen thousand, seven hundred forty-nine".