21102121165 has 16 divisors (see below), whose sum is σ = 27113376240. Its totient is φ = 15710126080.

The previous prime is 21102121153. The next prime is 21102121217. The reversal of 21102121165 is 56112120112.

It can be written as a sum of positive squares in 8 ways, for example, as 3396649 + 21098724516 = 1843^2 + 145254^2 .

It is not a de Polignac number, because 21102121165 - 2⁵ = 21102121133 is a prime.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 1387156 + ... + 1402285.

It is an arithmetic number, because the mean of its divisors is an integer number (1694586015).

Almost surely, 2^21102121165 is an apocalyptic number.

It is an amenable number.

21102121165 is a deficient number, since it is larger than the sum of its proper divisors (6011255075).

21102121165 is a wasteful number, since it uses less digits than its factorization.

21102121165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2789552.

The product of its (nonzero) digits is 240, while the sum is 22.

Adding to 21102121165 its reverse (56112120112), we get a palindrome (77214241277).

The spelling of 21102121165 in words is "twenty-one billion, one hundred two million, one hundred twenty-one thousand, one hundred sixty-five".