21001221200000 has 192 divisors, whose sum is σ = 52318886142600. Its totient is φ = 8396590080000.

The previous prime is 21001221199837. The next prime is 21001221200017. The reversal of 21001221200000 is 212210012.

It is a happy number.

It can be written as a sum of positive squares in 12 ways, for example, as 13055272051264 + 7945949148736 = 3613208^2 + 2818856^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 955589012 + ... + 955610988.

Almost surely, 2^{21001221200000} is an apocalyptic number.

21001221200000 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 21001221200000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26159443071300).

21001221200000 is an abundant number, since it is smaller than the sum of its proper divisors (31317664942600).

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

21001221200000 is an frugal number, since it uses more digits than its factorization.

21001221200000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24405 (or 24373 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21001221200000 its reverse (212210012), we get a palindrome (21001433410012).

The spelling of 21001221200000 in words is "twenty-one trillion, one billion, two hundred twenty-one million, two hundred thousand".