81947913599 has 4 divisors (see below), whose sum is σ = 81955328040. Its totient is φ = 81940499160.

The previous prime is 81947913587. The next prime is 81947913611. The reversal of 81947913599 is 99531974918.

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

It is an interprime number because it is at equal distance from previous prime (81947913587) and next prime (81947913611).

It is a cyclic number.

It is not a de Polignac number, because 81947913599 - 2⁴ = 81947913583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81947913199) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3690617 + ... + 3712754.

It is an arithmetic number, because the mean of its divisors is an integer number (20488832010).

Almost surely, 2^81947913599 is an apocalyptic number.

81947913599 is a deficient number, since it is larger than the sum of its proper divisors (7414441).

81947913599 is a wasteful number, since it uses less digits than its factorization.

81947913599 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7414440.

The product of its digits is 22044960, while the sum is 65.

The spelling of 81947913599 in words is "eighty-one billion, nine hundred forty-seven million, nine hundred thirteen thousand, five hundred ninety-nine".