21212020210121 has 24 divisors (see below), whose sum is σ = 24310874027160. Its totient is φ = 18334989130752.

The previous prime is 21212020210093. The next prime is 21212020210177. The reversal of 21212020210121 is 12101202021212.

It can be written as a sum of positive squares in 12 ways, for example, as 2859886854400 + 18352133355721 = 1691120^2 + 4283939^2 .

It is not a de Polignac number, because 21212020210121 - 2⁶ = 21212020210057 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21212020210121.

It is not an unprimeable number, because it can be changed into a prime (21212020210021) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7340195 + ... + 9813383.

It is an arithmetic number, because the mean of its divisors is an integer number (1012953084465).

Almost surely, 2^{21212020210121} is an apocalyptic number.

It is an amenable number.

21212020210121 is a deficient number, since it is larger than the sum of its proper divisors (3098853817039).

21212020210121 is a wasteful number, since it uses less digits than its factorization.

21212020210121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2473613 (or 2473416 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21212020210121 its reverse (12101202021212), we get a palindrome (33313222231333).

The spelling of 21212020210121 in words is "twenty-one trillion, two hundred twelve billion, twenty million, two hundred ten thousand, one hundred twenty-one".