21212100021 has 64 divisors (see below), whose sum is σ = 34144911360. Its totient is φ = 11458860480.

The previous prime is 21212100017. The next prime is 21212100031. The reversal of 21212100021 is 12000121212.

It is not a de Polignac number, because 21212100021 - 2² = 21212100017 is a prime.

It is a super-3 number, since 3×21212100021³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212100001) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 6412650 + ... + 6415956.

It is an arithmetic number, because the mean of its divisors is an integer number (533514240).

Almost surely, 2^21212100021 is an apocalyptic number.

21212100021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21212100021 is a deficient number, since it is larger than the sum of its proper divisors (12932811339).

21212100021 is a wasteful number, since it uses less digits than its factorization.

21212100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3574.

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

Adding to 21212100021 its reverse (12000121212), we get a palindrome (33212221233).

The spelling of 21212100021 in words is "twenty-one billion, two hundred twelve million, one hundred thousand, twenty-one".