81749523509 has 2 divisors, whose sum is σ = 81749523510. Its totient is φ = 81749523508.

The previous prime is 81749523439. The next prime is 81749523539. The reversal of 81749523509 is 90532594718.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79889326609 + 1860196900 = 282647^2 + 43130^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81749523509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81749523539) 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, 40874761754 + 40874761755.

It is an arithmetic number, because the mean of its divisors is an integer number (40874761755).

Almost surely, 2^81749523509 is an apocalyptic number.

It is an amenable number.

81749523509 is a deficient number, since it is larger than the sum of its proper divisors (1).

81749523509 is an equidigital number, since it uses as much as digits as its factorization.

81749523509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2721600, while the sum is 53.

The spelling of 81749523509 in words is "eighty-one billion, seven hundred forty-nine million, five hundred twenty-three thousand, five hundred nine".