21001220100220 has 48 divisors (see below), whose sum is σ = 44148255590880. Its totient is φ = 8391788996864.

The previous prime is 21001220100181. The next prime is 21001220100227. The reversal of 21001220100220 is 2200102210012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001220100220.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001220100227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 76323327 + ... + 76597993.

It is an arithmetic number, because the mean of its divisors is an integer number (919755324810).

Almost surely, 2^{21001220100220} is an apocalyptic number.

21001220100220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001220100220 is an abundant number, since it is smaller than the sum of its proper divisors (23147035490660).

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

21001220100220 is a wasteful number, since it uses less digits than its factorization.

21001220100220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278622 (or 278620 counting only the distinct ones).

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

Adding to 21001220100220 its reverse (2200102210012), we get a palindrome (23201322310232).

The spelling of 21001220100220 in words is "twenty-one trillion, one billion, two hundred twenty million, one hundred thousand, two hundred twenty".