81015287993 has 2 divisors, whose sum is σ = 81015287994. Its totient is φ = 81015287992.

The previous prime is 81015287939. The next prime is 81015288017. The reversal of 81015287993 is 39978251018.

It is a happy number.

Together with previous prime (81015287939) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69486541609 + 11528746384 = 263603^2 + 107372^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81015287993 is a prime.

It is not a weakly prime, because it can be changed into another prime (81015287933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40507643996 + 40507643997.

It is an arithmetic number, because the mean of its divisors is an integer number (40507643997).

Almost surely, 2^81015287993 is an apocalyptic number.

It is an amenable number.

81015287993 is a deficient number, since it is larger than the sum of its proper divisors (1).

81015287993 is an equidigital number, since it uses as much as digits as its factorization.

81015287993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1088640, while the sum is 53.

The spelling of 81015287993 in words is "eighty-one billion, fifteen million, two hundred eighty-seven thousand, nine hundred ninety-three".