21100121 has 4 divisors (see below), whose sum is σ = 24114432. Its totient is φ = 18085812.

The previous prime is 21100103. The next prime is 21100129. The reversal of 21100121 is 12100112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21100121 - 2¹⁰ = 21099097 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21100099 and 21100108.

It is not an unprimeable number, because it can be changed into a prime (21100129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1507145 + ... + 1507158.

It is an arithmetic number, because the mean of its divisors is an integer number (6028608).

Almost surely, 2^21100121 is an apocalyptic number.

It is an amenable number.

21100121 is a deficient number, since it is larger than the sum of its proper divisors (3014311).

21100121 is an equidigital number, since it uses as much as digits as its factorization.

21100121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3014310.

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 21100121 is about 4593.4868019839. The cubic root of 21100121 is about 276.3301770375.

Adding to 21100121 its reverse (12100112), we get a palindrome (33200233).

Subtracting from 21100121 its reverse (12100112), we obtain a palindrome (9000009).

The spelling of 21100121 in words is "twenty-one million, one hundred thousand, one hundred twenty-one".