81521175713 has 4 divisors (see below), whose sum is σ = 81907532208. Its totient is φ = 81134819220.

The previous prime is 81521175679. The next prime is 81521175739. The reversal of 81521175713 is 31757112518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81521175713 - 2¹⁴ = 81521159329 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81521175793) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 193177931 + ... + 193178352.

It is an arithmetic number, because the mean of its divisors is an integer number (20476883052).

Almost surely, 2^81521175713 is an apocalyptic number.

It is an amenable number.

81521175713 is a deficient number, since it is larger than the sum of its proper divisors (386356495).

81521175713 is a wasteful number, since it uses less digits than its factorization.

81521175713 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386356494.

The product of its digits is 58800, while the sum is 41.

The spelling of 81521175713 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, seven hundred thirteen".