1991440 has 80 divisors (see below), whose sum is σ = 5285376. Its totient is φ = 691200.

The previous prime is 1991413. The next prime is 1991443. The reversal of 1991440 is 441991.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 1991399 and 1991408.

It is not an unprimeable number, because it can be changed into a prime (1991443) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27244 + ... + 27316.

2^1991440 is an apocalyptic number.

1991440 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 1991440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2642688).

1991440 is an abundant number, since it is smaller than the sum of its proper divisors (3293936).

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

1991440 is a wasteful number, since it uses less digits than its factorization.

1991440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128 (or 122 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 28.

The square root of 1991440 is about 1411.1839001349. The cubic root of 1991440 is about 125.8120992000.

The spelling of 1991440 in words is "one million, nine hundred ninety-one thousand, four hundred forty".