21245220544 has 56 divisors (see below), whose sum is σ = 42911914176. Its totient is φ = 10433280000.

The previous prime is 21245220533. The next prime is 21245220593. The reversal of 21245220544 is 44502254212.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2967369 + ... + 2974519.

Almost surely, 2^21245220544 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21245220544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21455957088).

21245220544 is an abundant number, since it is smaller than the sum of its proper divisors (21666693632).

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

21245220544 is an equidigital number, since it uses as much as digits as its factorization.

21245220544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7985 (or 7975 counting only the distinct ones).

The product of its (nonzero) digits is 25600, while the sum is 31.

Adding to 21245220544 its reverse (44502254212), we get a palindrome (65747474756).

The spelling of 21245220544 in words is "twenty-one billion, two hundred forty-five million, two hundred twenty thousand, five hundred forty-four".