21100100121 has 24 divisors (see below), whose sum is σ = 31654162176. Its totient is φ = 13529423520.

The previous prime is 21100100093. The next prime is 21100100143. The reversal of 21100100121 is 12100100112.

It is a happy number.

It is not a de Polignac number, because 21100100121 - 2⁶ = 21100100057 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21100100221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 186510 + ... + 277463.

It is an arithmetic number, because the mean of its divisors is an integer number (1318923424).

Almost surely, 2^21100100121 is an apocalyptic number.

It is an amenable number.

21100100121 is a deficient number, since it is larger than the sum of its proper divisors (10554062055).

21100100121 is a wasteful number, since it uses less digits than its factorization.

21100100121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 464173 (or 464170 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21100100121 its reverse (12100100112), we get a palindrome (33200200233).

Subtracting from 21100100121 its reverse (12100100112), we obtain a palindrome (9000000009).

The spelling of 21100100121 in words is "twenty-one billion, one hundred million, one hundred thousand, one hundred twenty-one".