81521175293 has 8 divisors (see below), whose sum is σ = 81883166400. Its totient is φ = 81159978528.

The previous prime is 81521175289. The next prime is 81521175311. The reversal of 81521175293 is 39257112518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81521175293 - 2² = 81521175289 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent 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 7 ways as a sum of consecutive naturals, for example, 7598 + ... + 403856.

It is an arithmetic number, because the mean of its divisors is an integer number (10235395800).

Almost surely, 2^81521175293 is an apocalyptic number.

It is an amenable number.

81521175293 is a deficient number, since it is larger than the sum of its proper divisors (361991107).

81521175293 is a wasteful number, since it uses less digits than its factorization.

81521175293 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 397171.

The product of its digits is 151200, while the sum is 44.

The spelling of 81521175293 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, two hundred ninety-three".