21100020121 has 4 divisors (see below), whose sum is σ = 21101145700. Its totient is φ = 21098894544.

The previous prime is 21100020107. The next prime is 21100020143. The reversal of 21100020121 is 12102000112.

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 10395841600 + 10704178521 = 101960^2 + 103461^2 .

It is a cyclic number.

It is not a de Polignac number, because 21100020121 - 2¹⁵ = 21099987353 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21100020098 and 21100020107.

It is not an unprimeable number, because it can be changed into a prime (21100027121) 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, 534186 + ... + 572323.

It is an arithmetic number, because the mean of its divisors is an integer number (5275286425).

Almost surely, 2^21100020121 is an apocalyptic number.

It is an amenable number.

21100020121 is a deficient number, since it is larger than the sum of its proper divisors (1125579).

21100020121 is a wasteful number, since it uses less digits than its factorization.

21100020121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1125578.

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

Adding to 21100020121 its reverse (12102000112), we get a palindrome (33202020233).

The spelling of 21100020121 in words is "twenty-one billion, one hundred million, twenty thousand, one hundred twenty-one".