19981800 has 144 divisors (see below), whose sum is σ = 71161740. Its totient is φ = 5007360.

The previous prime is 19981777. The next prime is 19981807. The reversal of 19981800 is 818991.

It can be written as a sum of positive squares in 6 ways, for example, as 7322436 + 12659364 = 2706^2 + 3558^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (19981807) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 30274 + ... + 30926.

Almost surely, 2^19981800 is an apocalyptic number.

19981800 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 19981800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35580870).

19981800 is an abundant number, since it is smaller than the sum of its proper divisors (51179940).

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

19981800 is a wasteful number, since it uses less digits than its factorization.

19981800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 692 (or 680 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 36.

The square root of 19981800 is about 4470.1006700073. The cubic root of 19981800 is about 271.3593993368.

The spelling of 19981800 in words is "nineteen million, nine hundred eighty-one thousand, eight hundred".