21120012020021 has 4 divisors (see below), whose sum is σ = 21120043676844. Its totient is φ = 21119980363200.

The previous prime is 21120012020017. The next prime is 21120012020039. The reversal of 21120012020021 is 12002021002112.

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 9926878983025 + 11193133036996 = 3150695^2 + 3345614^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120012020021 - 2² = 21120012020017 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21120012019978 and 21120012020005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21120012020321) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14805650 + ... + 16169331.

It is an arithmetic number, because the mean of its divisors is an integer number (5280010919211).

Almost surely, 2^{21120012020021} is an apocalyptic number.

It is an amenable number.

21120012020021 is a deficient number, since it is larger than the sum of its proper divisors (31656823).

21120012020021 is an equidigital number, since it uses as much as digits as its factorization.

21120012020021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31656822.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21120012020021 its reverse (12002021002112), we get a palindrome (33122033022133).

The spelling of 21120012020021 in words is "twenty-one trillion, one hundred twenty billion, twelve million, twenty thousand, twenty-one".