21200002121 has 4 divisors (see below), whose sum is σ = 21200335044. Its totient is φ = 21199669200.

The previous prime is 21200002097. The next prime is 21200002151. The reversal of 21200002121 is 12120000212.

It is a happy number.

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 20068688896 + 1131313225 = 141664^2 + 33635^2 .

It is a cyclic number.

It is not a de Polignac number, because 21200002121 - 2²² = 21195807817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21200002151) 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, 37790 + ... + 209351.

It is an arithmetic number, because the mean of its divisors is an integer number (5300083761).

Almost surely, 2^21200002121 is an apocalyptic number.

It is an amenable number.

21200002121 is a deficient number, since it is larger than the sum of its proper divisors (332923).

21200002121 is an equidigital number, since it uses as much as digits as its factorization.

21200002121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332922.

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

Adding to 21200002121 its reverse (12120000212), we get a palindrome (33320002333).

The spelling of 21200002121 in words is "twenty-one billion, two hundred million, two thousand, one hundred twenty-one".