81609958499 has 4 divisors (see below), whose sum is σ = 81648293160. Its totient is φ = 81571623840.

The previous prime is 81609958457. The next prime is 81609958537. The reversal of 81609958499 is 99485990618.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81609958499 - 2¹² = 81609954403 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81609958429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19164137 + ... + 19168394.

It is an arithmetic number, because the mean of its divisors is an integer number (20412073290).

Almost surely, 2^81609958499 is an apocalyptic number.

81609958499 is a deficient number, since it is larger than the sum of its proper divisors (38334661).

81609958499 is a wasteful number, since it uses less digits than its factorization.

81609958499 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38334660.

The product of its (nonzero) digits is 50388480, while the sum is 68.

The spelling of 81609958499 in words is "eighty-one billion, six hundred nine million, nine hundred fifty-eight thousand, four hundred ninety-nine".