81521288315 has 4 divisors (see below), whose sum is σ = 97825545984. Its totient is φ = 65217030648.

The previous prime is 81521288281. The next prime is 81521288323. The reversal of 81521288315 is 51388212518.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81521288315 - 2²⁰ = 81520239739 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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, 8152128827 + ... + 8152128836.

It is an arithmetic number, because the mean of its divisors is an integer number (24456386496).

Almost surely, 2^81521288315 is an apocalyptic number.

81521288315 is a deficient number, since it is larger than the sum of its proper divisors (16304257669).

81521288315 is a wasteful number, since it uses less digits than its factorization.

81521288315 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16304257668.

The product of its digits is 153600, while the sum is 44.

The spelling of 81521288315 in words is "eighty-one billion, five hundred twenty-one million, two hundred eighty-eight thousand, three hundred fifteen".