71809537991 has 4 divisors (see below), whose sum is σ = 72374967552. Its totient is φ = 71244108432.

The previous prime is 71809537931. The next prime is 71809537993. The reversal of 71809537991 is 19973590817.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19973590817 = 2683 ⋅7444499.

It is a cyclic number.

It is not a de Polignac number, because 71809537991 - 2¹⁸ = 71809275847 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 71809537991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (71809537993) 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 3 ways as a sum of consecutive naturals, for example, 282714590 + ... + 282714843.

It is an arithmetic number, because the mean of its divisors is an integer number (18093741888).

Almost surely, 2^71809537991 is an apocalyptic number.

71809537991 is a deficient number, since it is larger than the sum of its proper divisors (565429561).

71809537991 is a wasteful number, since it uses less digits than its factorization.

71809537991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 565429560.

The product of its (nonzero) digits is 4286520, while the sum is 59.

The spelling of 71809537991 in words is "seventy-one billion, eight hundred nine million, five hundred thirty-seven thousand, nine hundred ninety-one".