81479947991 has 16 divisors (see below), whose sum is σ = 90831857760. Its totient is φ = 72571981440.

The previous prime is 81479947981. The next prime is 81479947993. The reversal of 81479947991 is 19974997418.

It is a cyclic number.

It is not a de Polignac number, because 81479947991 - 2¹⁰ = 81479946967 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 (81479947993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 523481 + ... + 661053.

It is an arithmetic number, because the mean of its divisors is an integer number (5676991110).

Almost surely, 2^81479947991 is an apocalyptic number.

81479947991 is a deficient number, since it is larger than the sum of its proper divisors (9351909769).

81479947991 is a wasteful number, since it uses less digits than its factorization.

81479947991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139186.

The product of its digits is 41150592, while the sum is 68.

The spelling of 81479947991 in words is "eighty-one billion, four hundred seventy-nine million, nine hundred forty-seven thousand, nine hundred ninety-one".