81179515921 has 8 divisors (see below), whose sum is σ = 94750560000. Its totient is φ = 68101964448.

The previous prime is 81179515867. The next prime is 81179515939. The reversal of 81179515921 is 12951597118.

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

It is not a de Polignac number, because 81179515921 - 2¹³ = 81179507729 is a prime.

It is a super-2 number, since 2×81179515921² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81179510921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 123372796 + ... + 123373453.

It is an arithmetic number, because the mean of its divisors is an integer number (11843820000).

Almost surely, 2^81179515921 is an apocalyptic number.

It is an amenable number.

81179515921 is a deficient number, since it is larger than the sum of its proper divisors (13571044079).

81179515921 is a wasteful number, since it uses less digits than its factorization.

81179515921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 246746303.

The product of its digits is 226800, while the sum is 49.

The spelling of 81179515921 in words is "eighty-one billion, one hundred seventy-nine million, five hundred fifteen thousand, nine hundred twenty-one".