1991406 has 16 divisors (see below), whose sum is σ = 4048848. Its totient is φ = 652800.

The previous prime is 1991389. The next prime is 1991413. The reversal of 1991406 is 6041991.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2355 + ... + 3086.

It is an arithmetic number, because the mean of its divisors is an integer number (253053).

2^1991406 is an apocalyptic number.

1991406 is an abundant number, since it is smaller than the sum of its proper divisors (2057442).

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

1991406 is a wasteful number, since it uses less digits than its factorization.

1991406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5507.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 1991406 is about 1411.1718534608. The cubic root of 1991406 is about 125.8113831962.

The spelling of 1991406 in words is "one million, nine hundred ninety-one thousand, four hundred six".