21212122120 has 128 divisors (see below), whose sum is σ = 57474720000. Its totient is φ = 6882941952.

The previous prime is 21212122081. The next prime is 21212122187. The reversal of 21212122120 is 2122121212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21212122094 and 21212122103.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8877886 + ... + 8880274.

It is an arithmetic number, because the mean of its divisors is an integer number (449021250).

Almost surely, 2^21212122120 is an apocalyptic number.

21212122120 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 21212122120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28737360000).

21212122120 is an abundant number, since it is smaller than the sum of its proper divisors (36262597880).

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

21212122120 is a wasteful number, since it uses less digits than its factorization.

21212122120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4095 (or 4091 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21212122120 its reverse (2122121212), we get a palindrome (23334243332).

The spelling of 21212122120 in words is "twenty-one billion, two hundred twelve million, one hundred twenty-two thousand, one hundred twenty".