21122515165 has 4 divisors (see below), whose sum is σ = 25347018204. Its totient is φ = 16898012128.

The previous prime is 21122515163. The next prime is 21122515217. The reversal of 21122515165 is 56151522112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10232131716 + 10890383449 = 101154^2 + 104357^2 .

It is a cyclic number.

It is not a de Polignac number, because 21122515165 - 2¹ = 21122515163 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122515163) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2112251512 + ... + 2112251521.

It is an arithmetic number, because the mean of its divisors is an integer number (6336754551).

Almost surely, 2^21122515165 is an apocalyptic number.

It is an amenable number.

21122515165 is a deficient number, since it is larger than the sum of its proper divisors (4224503039).

21122515165 is an equidigital number, since it uses as much as digits as its factorization.

21122515165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4224503038.

The product of its digits is 6000, while the sum is 31.

The spelling of 21122515165 in words is "twenty-one billion, one hundred twenty-two million, five hundred fifteen thousand, one hundred sixty-five".