18399780 has 144 divisors (see below), whose sum is σ = 67616640. Its totient is φ = 3953664.

The previous prime is 18399751. The next prime is 18399781. The reversal of 18399780 is 8799381.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (18399781) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 20991 + ... + 21849.

It is an arithmetic number, because the mean of its divisors is an integer number (469560).

Almost surely, 2^18399780 is an apocalyptic number.

18399780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18399780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33808320).

18399780 is an abundant number, since it is smaller than the sum of its proper divisors (49216860).

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

18399780 is a wasteful number, since it uses less digits than its factorization.

18399780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 898 (or 893 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 18399780 is about 4289.4964739466. The cubic root of 18399780 is about 264.0001721762. Note that the first 3 decimals are identical.

The spelling of 18399780 in words is "eighteen million, three hundred ninety-nine thousand, seven hundred eighty".