21521447200 has 108 divisors (see below), whose sum is σ = 57749995170. Its totient is φ = 7825945600.

The previous prime is 21521447197. The next prime is 21521447221. The reversal of 21521447200 is 274412512.

It can be written as a sum of positive squares in 3 ways, for example, as 15059216656 + 6462230544 = 122716^2 + 80388^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 14365 + ... + 207964.

Almost surely, 2^21521447200 is an apocalyptic number.

21521447200 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 21521447200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28874997585).

21521447200 is an abundant number, since it is smaller than the sum of its proper divisors (36228547970).

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

21521447200 is a wasteful number, since it uses less digits than its factorization.

21521447200 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222371 (or 222347 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 28.

Adding to 21521447200 its reverse (274412512), we get a palindrome (21795859712).

The spelling of 21521447200 in words is "twenty-one billion, five hundred twenty-one million, four hundred forty-seven thousand, two hundred".