21001200000 has 768 divisors, whose sum is σ = 79937383680. Its totient is φ = 4838400000.

The previous prime is 21001199993. The next prime is 21001200001. The reversal of 21001200000 is 210012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (6).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001200001) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 488399979 + ... + 488400021.

It is an arithmetic number, because the mean of its divisors is an integer number (104085135).

Almost surely, 2^21001200000 is an apocalyptic number.

21001200000 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 21001200000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39968691840).

21001200000 is an abundant number, since it is smaller than the sum of its proper divisors (58936183680).

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

21001200000 is an equidigital number, since it uses as much as digits as its factorization.

21001200000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133 (or 101 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 6.

Adding to 21001200000 its reverse (210012), we get a palindrome (21001410012).

21001200000 divided by its reverse (210012) gives a 5-th power (100000 = 10⁵).

The spelling of 21001200000 in words is "twenty-one billion, one million, two hundred thousand".