21001220122120 has 128 divisors (see below), whose sum is σ = 54591979299840. Its totient is φ = 7122324867840.

The previous prime is 21001220122109. The next prime is 21001220122139. The reversal of 21001220122120 is 2122102210012.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21001220122094 and 21001220122103.

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, 8539639 + ... + 10720441.

It is an arithmetic number, because the mean of its divisors is an integer number (426499838280).

Almost surely, 2^{21001220122120} is an apocalyptic number.

21001220122120 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 21001220122120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27295989649920).

21001220122120 is an abundant number, since it is smaller than the sum of its proper divisors (33590759177720).

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

21001220122120 is a wasteful number, since it uses less digits than its factorization.

21001220122120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2181195 (or 2181191 counting only the distinct ones).

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

Adding to 21001220122120 its reverse (2122102210012), we get a palindrome (23123322332132).

The spelling of 21001220122120 in words is "twenty-one trillion, one billion, two hundred twenty million, one hundred twenty-two thousand, one hundred twenty".