18021988516 has 81 divisors (see below), whose sum is σ = 37729850571. Its totient is φ = 7510258224.

The previous prime is 18021988511. The next prime is 18021988519. The reversal of 18021988516 is 61588912081.

The square root of 18021988516 is 134246.

It is a perfect power (a square), and thus also a powerful number.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a self number, because there is not a number n which added to its sum of digits gives 18021988516.

It is not an unprimeable number, because it can be changed into a prime (18021988511) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 80815981 + ... + 80816203.

Almost surely, 2^18021988516 is an apocalyptic number.

18021988516 is the 134246-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18021988516

18021988516 is an abundant number, since it is smaller than the sum of its proper divisors (19707862055).

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

18021988516 is an equidigital number, since it uses as much as digits as its factorization.

18021988516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 550 (or 275 counting only the distinct ones).

The product of its (nonzero) digits is 276480, while the sum is 49.

Multiplying 18021988516 by its sum of digits (49), we get a square (883077437284 = 939722²).

18021988516 divided by its sum of digits (49) gives a square (367795684 = 19178²).

The spelling of 18021988516 in words is "eighteen billion, twenty-one million, nine hundred eighty-eight thousand, five hundred sixteen".