2121200021 has 2 divisors, whose sum is σ = 2121200022. Its totient is φ = 2121200020.

The previous prime is 2121199999. The next prime is 2121200023. The reversal of 2121200021 is 1200021212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1210065796 + 911134225 = 34786^2 + 30185^2 .

It is a cyclic number.

It is not a de Polignac number, because 2121200021 - 2¹⁸ = 2120937877 is a prime.

Together with 2121200023, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 2121199975 and 2121200011.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2121200023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1060600010 + 1060600011.

It is an arithmetic number, because the mean of its divisors is an integer number (1060600011).

Almost surely, 2^2121200021 is an apocalyptic number.

It is an amenable number.

2121200021 is a deficient number, since it is larger than the sum of its proper divisors (1).

2121200021 is an equidigital number, since it uses as much as digits as its factorization.

2121200021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 2121200021 is about 46056.4872846378. The cubic root of 2121200021 is about 1284.8739995659.

Adding to 2121200021 its reverse (1200021212), we get a palindrome (3321221233).

It can be divided in two parts, 212 and 1200021, that multiplied together give a palindrome (254404452).

The spelling of 2121200021 in words is "two billion, one hundred twenty-one million, two hundred thousand, twenty-one".