21210121100021 has 12 divisors (see below), whose sum is σ = 25583082358752. Its totient is φ = 17223256229544.

The previous prime is 21210121100011. The next prime is 21210121100033. The reversal of 21210121100021 is 12000112101212.

It is a de Polignac number, because none of the positive numbers 2^k-21210121100021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210121099969 and 21210121100005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210121100011) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4196697335 + ... + 4196702388.

It is an arithmetic number, because the mean of its divisors is an integer number (2131923529896).

Almost surely, 2^{21210121100021} is an apocalyptic number.

It is an amenable number.

21210121100021 is a deficient number, since it is larger than the sum of its proper divisors (4372961258731).

21210121100021 is an equidigital number, since it uses as much as digits as its factorization.

21210121100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8393399768 (or 8393399749 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21210121100021 its reverse (12000112101212), we get a palindrome (33210233201233).

The spelling of 21210121100021 in words is "twenty-one trillion, two hundred ten billion, one hundred twenty-one million, one hundred thousand, twenty-one".