21001121201220 has 384 divisors, whose sum is σ = 67098070351872. Its totient is φ = 4876658688000.

The previous prime is 21001121201219. The next prime is 21001121201227. The reversal of 21001121201220 is 2210212110012.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21001121201220.

It is not an unprimeable number, because it can be changed into a prime (21001121201227) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 1779599320 + ... + 1779611120.

It is an arithmetic number, because the mean of its divisors is an integer number (174734558208).

Almost surely, 2^{21001121201220} is an apocalyptic number.

21001121201220 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 21001121201220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33549035175936).

21001121201220 is an abundant number, since it is smaller than the sum of its proper divisors (46096949150652).

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

21001121201220 is a wasteful number, since it uses less digits than its factorization.

21001121201220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14331 (or 14329 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21001121201220 its reverse (2210212110012), we get a palindrome (23211333311232).

The spelling of 21001121201220 in words is "twenty-one trillion, one billion, one hundred twenty-one million, two hundred one thousand, two hundred twenty".