12815081721 has 24 divisors (see below), whose sum is σ = 20008726920. Its totient is φ = 7856868096.

The previous prime is 12815081717. The next prime is 12815081731. The reversal of 12815081721 is 12718051821.

12815081721 is a `hidden beast` number, since 1 + 2 + 81 + 508 + 1 + 72 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 15327225 + 12799754496 = 3915^2 + 113136^2 .

It is not a de Polignac number, because 12815081721 - 2² = 12815081717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (12815081731) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 172116 + ... + 235061.

It is an arithmetic number, because the mean of its divisors is an integer number (833696955).

Almost surely, 2^12815081721 is an apocalyptic number.

It is an amenable number.

12815081721 is a deficient number, since it is larger than the sum of its proper divisors (7193645199).

12815081721 is a wasteful number, since it uses less digits than its factorization.

12815081721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407465 (or 407462 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 36.

The spelling of 12815081721 in words is "twelve billion, eight hundred fifteen million, eighty-one thousand, seven hundred twenty-one".