21000121200 has 180 divisors, whose sum is σ = 73248657768. Its totient is φ = 5571417600.

The previous prime is 21000121187. The next prime is 21000121211. The reversal of 21000121200 is 212100012.

It is a tau number, because it is divible by the number of its divisors (180).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 694395 + ... + 724005.

Almost surely, 2^21000121200 is an apocalyptic number.

21000121200 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 21000121200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36624328884).

21000121200 is an abundant number, since it is smaller than the sum of its proper divisors (52248536568).

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

21000121200 is a wasteful number, since it uses less digits than its factorization.

21000121200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29832 (or 29818 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21000121200 its reverse (212100012), we get a palindrome (21212221212).

The spelling of 21000121200 in words is "twenty-one billion, one hundred twenty-one thousand, two hundred".