21001202121 has 16 divisors (see below), whose sum is σ = 28297942400. Its totient is φ = 13853410560.

The previous prime is 21001202099. The next prime is 21001202129. The reversal of 21001202121 is 12120210012.

It is not a de Polignac number, because 21001202121 - 2¹⁹ = 21000677833 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001202097 and 21001202106.

It is not an unprimeable number, because it can be changed into a prime (21001202129) 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, 10881 + ... + 205233.

It is an arithmetic number, because the mean of its divisors is an integer number (1768621400).

Almost surely, 2^21001202121 is an apocalyptic number.

It is an amenable number.

21001202121 is a deficient number, since it is larger than the sum of its proper divisors (7296740279).

21001202121 is a wasteful number, since it uses less digits than its factorization.

21001202121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194736.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001202121 its reverse (12120210012), we get a palindrome (33121412133).

The spelling of 21001202121 in words is "twenty-one billion, one million, two hundred two thousand, one hundred twenty-one".