21155012224 has 64 divisors (see below), whose sum is σ = 44970984000. Its totient is φ = 9883441152.

The previous prime is 21155012209. The next prime is 21155012227. The reversal of 21155012224 is 42221055112.

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (21155012227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 117957 + ... + 237115.

It is an arithmetic number, because the mean of its divisors is an integer number (702671625).

Almost surely, 2^21155012224 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 21155012224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22485492000).

21155012224 is an abundant number, since it is smaller than the sum of its proper divisors (23815971776).

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

21155012224 is a wasteful number, since it uses less digits than its factorization.

21155012224 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119265 (or 119253 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

Adding to 21155012224 its reverse (42221055112), we get a palindrome (63376067336).

The spelling of 21155012224 in words is "twenty-one billion, one hundred fifty-five million, twelve thousand, two hundred twenty-four".