21516916218 has 128 divisors (see below), whose sum is σ = 52986286080. Its totient is φ = 5685335040.

The previous prime is 21516916181. The next prime is 21516916247. The reversal of 21516916218 is 81261961512.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21516916218.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 21240280 + ... + 21241292.

It is an arithmetic number, because the mean of its divisors is an integer number (413955360).

Almost surely, 2^21516916218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21516916218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26493143040).

21516916218 is an abundant number, since it is smaller than the sum of its proper divisors (31469369862).

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

21516916218 is a wasteful number, since it uses less digits than its factorization.

21516916218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1532.

The product of its digits is 51840, while the sum is 42.

The spelling of 21516916218 in words is "twenty-one billion, five hundred sixteen million, nine hundred sixteen thousand, two hundred eighteen".