81815765249 has 2 divisors, whose sum is σ = 81815765250. Its totient is φ = 81815765248.

The previous prime is 81815765219. The next prime is 81815765257. The reversal of 81815765249 is 94256751818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64861902400 + 16953862849 = 254680^2 + 130207^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81815765249 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81815765194 and 81815765203.

It is not a weakly prime, because it can be changed into another prime (81815765219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40907882624 + 40907882625.

It is an arithmetic number, because the mean of its divisors is an integer number (40907882625).

Almost surely, 2^81815765249 is an apocalyptic number.

It is an amenable number.

81815765249 is a deficient number, since it is larger than the sum of its proper divisors (1).

81815765249 is an equidigital number, since it uses as much as digits as its factorization.

81815765249 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4838400, while the sum is 56.

The spelling of 81815765249 in words is "eighty-one billion, eight hundred fifteen million, seven hundred sixty-five thousand, two hundred forty-nine".