21255115518 has 192 divisors, whose sum is σ = 57890851200. Its totient is φ = 5487243264.

The previous prime is 21255115517. The next prime is 21255115523. The reversal of 21255115518 is 81551155212.

It is a happy number.

21255115518 is a `hidden beast` number, since 2 + 1 + 25 + 5 + 115 + 518 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21255115517) 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, 17815930 + ... + 17817122.

It is an arithmetic number, because the mean of its divisors is an integer number (301514850).

Almost surely, 2^21255115518 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21255115518, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28945425600).

21255115518 is an abundant number, since it is smaller than the sum of its proper divisors (36635735682).

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

21255115518 is a wasteful number, since it uses less digits than its factorization.

21255115518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1443 (or 1440 counting only the distinct ones).

The product of its digits is 20000, while the sum is 36.

The spelling of 21255115518 in words is "twenty-one billion, two hundred fifty-five million, one hundred fifteen thousand, five hundred eighteen".