1981728 has 72 divisors (see below), whose sum is σ = 6447168. Its totient is φ = 565632.

The previous prime is 1981711. The next prime is 1981739. The reversal of 1981728 is 8271891.

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 1981692 and 1981701.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1525 + ... + 2507.

It is an arithmetic number, because the mean of its divisors is an integer number (89544).

2^1981728 is an apocalyptic number.

1981728 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 1981728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3223584).

1981728 is an abundant number, since it is smaller than the sum of its proper divisors (4465440).

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

1981728 is a wasteful number, since it uses less digits than its factorization.

1981728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1006 (or 995 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 1981728 is about 1407.7386121010. The cubic root of 1981728 is about 125.6072426078.

The spelling of 1981728 in words is "one million, nine hundred eighty-one thousand, seven hundred twenty-eight".