81909708517 has 16 divisors (see below), whose sum is σ = 101168206720. Its totient is φ = 64578658752.

The previous prime is 81909708511. The next prime is 81909708539. The reversal of 81909708517 is 71580790918.

It is a cyclic number.

It is not a de Polignac number, because 81909708517 - 2¹⁹ = 81909184229 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81909708511) 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 in 15 ways as a sum of consecutive naturals, for example, 1564542 + ... + 1616047.

It is an arithmetic number, because the mean of its divisors is an integer number (6323012920).

Almost surely, 2^81909708517 is an apocalyptic number.

It is an amenable number.

81909708517 is a deficient number, since it is larger than the sum of its proper divisors (19258498203).

81909708517 is a wasteful number, since it uses less digits than its factorization.

81909708517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3180892.

The product of its (nonzero) digits is 1270080, while the sum is 55.

The spelling of 81909708517 in words is "eighty-one billion, nine hundred nine million, seven hundred eight thousand, five hundred seventeen".