21281712815 has 32 divisors (see below), whose sum is σ = 28782508032. Its totient is φ = 14965776000.

The previous prime is 21281712811. The next prime is 21281712817. The reversal of 21281712815 is 51821718212.

It is not a de Polignac number, because 21281712815 - 2² = 21281712811 is a prime.

It is a super-2 number, since 2×21281712815² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21281712811) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2336420 + ... + 2345510.

It is an arithmetic number, because the mean of its divisors is an integer number (899453376).

Almost surely, 2^21281712815 is an apocalyptic number.

21281712815 is a deficient number, since it is larger than the sum of its proper divisors (7500795217).

21281712815 is a wasteful number, since it uses less digits than its factorization.

21281712815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10511.

The product of its digits is 17920, while the sum is 38.

The spelling of 21281712815 in words is "twenty-one billion, two hundred eighty-one million, seven hundred twelve thousand, eight hundred fifteen".