21212112121020 has 240 divisors, whose sum is σ = 66671765455680. Its totient is φ = 5645641752576.

The previous prime is 21212112121009. The next prime is 21212112121037. The reversal of 21212112121020 is 2012121121212.

21212112121020 is a `hidden beast` number, since 212 + 1 + 211 + 212 + 10 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21212112120984 and 21212112121002.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 3040287772 + ... + 3040294748.

It is an arithmetic number, because the mean of its divisors is an integer number (277799022732).

Almost surely, 2^{21212112121020} is an apocalyptic number.

21212112121020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21212112121020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33335882727840).

21212112121020 is an abundant number, since it is smaller than the sum of its proper divisors (45459653334660).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21212112121020 is a wasteful number, since it uses less digits than its factorization.

21212112121020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10354 (or 10343 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 21212112121020 its reverse (2012121121212), we get a palindrome (23224233242232).

The spelling of 21212112121020 in words is "twenty-one trillion, two hundred twelve billion, one hundred twelve million, one hundred twenty-one thousand, twenty".