21200100121 has 4 divisors (see below), whose sum is σ = 22447164852. Its totient is φ = 19953035392.

The previous prime is 21200100043. The next prime is 21200100137. The reversal of 21200100121 is 12100100212.

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 8529446025 + 12670654096 = 92355^2 + 112564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21200100121 - 2⁷ = 21200099993 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21200100098 and 21200100107.

It is not an unprimeable number, because it can be changed into a prime (21200100161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 623532340 + ... + 623532373.

It is an arithmetic number, because the mean of its divisors is an integer number (5611791213).

Almost surely, 2^21200100121 is an apocalyptic number.

It is an amenable number.

21200100121 is a deficient number, since it is larger than the sum of its proper divisors (1247064731).

21200100121 is a wasteful number, since it uses less digits than its factorization.

21200100121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1247064730.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21200100121 its reverse (12100100212), we get a palindrome (33300200333).

Subtracting from 21200100121 its reverse (12100100212), we obtain a palindrome (9099999909).

The spelling of 21200100121 in words is "twenty-one billion, two hundred million, one hundred thousand, one hundred twenty-one".