21201210121 has 16 divisors (see below), whose sum is σ = 26148326400. Its totient is φ = 16739529408.

The previous prime is 21201210091. The next prime is 21201210133. The reversal of 21201210121 is 12101210212.

It is not a de Polignac number, because 21201210121 - 2⁷ = 21201209993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is not an unprimeable number, because it can be changed into a prime (21201210721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 199606 + ... + 286783.

It is an arithmetic number, because the mean of its divisors is an integer number (1634270400).

Almost surely, 2^21201210121 is an apocalyptic number.

It is an amenable number.

21201210121 is a deficient number, since it is larger than the sum of its proper divisors (4947116279).

21201210121 is a wasteful number, since it uses less digits than its factorization.

21201210121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486888.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21201210121 its reverse (12101210212), we get a palindrome (33302420333).

Subtracting from 21201210121 its reverse (12101210212), we obtain a palindrome (9099999909).

The spelling of 21201210121 in words is "twenty-one billion, two hundred one million, two hundred ten thousand, one hundred twenty-one".