21201221020 has 96 divisors (see below), whose sum is σ = 52157952000. Its totient is φ = 7235871552.

The previous prime is 21201220981. The next prime is 21201221021. The reversal of 21201221020 is 2012210212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201221021) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1522851 + ... + 1536709.

It is an arithmetic number, because the mean of its divisors is an integer number (543312000).

Almost surely, 2^21201221020 is an apocalyptic number.

21201221020 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 21201221020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26078976000).

21201221020 is an abundant number, since it is smaller than the sum of its proper divisors (30956730980).

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

21201221020 is a wasteful number, since it uses less digits than its factorization.

21201221020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14112 (or 14096 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21201221020 its reverse (2012210212), we get a palindrome (23213431232).

The spelling of 21201221020 in words is "twenty-one billion, two hundred one million, two hundred twenty-one thousand, twenty".