19981728 has 120 divisors (see below), whose sum is σ = 63392868. Its totient is φ = 6137856.

The previous prime is 19981727. The next prime is 19981757. The reversal of 19981728 is 82718991.

It can be written as a sum of positive squares in 2 ways, for example, as 19607184 + 374544 = 4428^2 + 612^2 .

It is not an unprimeable number, because it can be changed into a prime (19981723) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 33400 + ... + 33992.

Almost surely, 2^19981728 is an apocalyptic number.

19981728 is a gapful number since it is divisible by the number (18) 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 19981728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31696434).

19981728 is an abundant number, since it is smaller than the sum of its proper divisors (43411140).

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

19981728 is a wasteful number, since it uses less digits than its factorization.

19981728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 628 (or 611 counting only the distinct ones).

The product of its digits is 72576, while the sum is 45.

The square root of 19981728 is about 4470.0926164902. The cubic root of 19981728 is about 271.3590734086.

The spelling of 19981728 in words is "nineteen million, nine hundred eighty-one thousand, seven hundred twenty-eight".