21253212165121 has 4 divisors (see below), whose sum is σ = 21263083608132. Its totient is φ = 21243340722112.

The previous prime is 21253212165083. The next prime is 21253212165131. The reversal of 21253212165121 is 12156121235212.

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 12653280551025 + 8599931614096 = 3557145^2 + 2932564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253212165121 - 2³⁷ = 21115773211649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253212165131) 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 3 ways as a sum of consecutive naturals, for example, 4935718276 + ... + 4935722581.

It is an arithmetic number, because the mean of its divisors is an integer number (5315770902033).

Almost surely, 2^{21253212165121} is an apocalyptic number.

It is an amenable number.

21253212165121 is a deficient number, since it is larger than the sum of its proper divisors (9871443011).

21253212165121 is an equidigital number, since it uses as much as digits as its factorization.

21253212165121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9871443010.

The product of its digits is 14400, while the sum is 34.

The spelling of 21253212165121 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred twelve million, one hundred sixty-five thousand, one hundred twenty-one".