1991906 has 16 divisors (see below), whose sum is σ = 3459840. Its totient is φ = 842400.

The previous prime is 1991893. The next prime is 1991911. The reversal of 1991906 is 6091991.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 206 + ... + 2006.

It is an arithmetic number, because the mean of its divisors is an integer number (216240).

2^1991906 is an apocalyptic number.

1991906 is a deficient number, since it is larger than the sum of its proper divisors (1467934).

1991906 is a wasteful number, since it uses less digits than its factorization.

1991906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1889.

The product of its (nonzero) digits is 4374, while the sum is 35.

The square root of 1991906 is about 1411.3490000705. The cubic root of 1991906 is about 125.8219118424.

The spelling of 1991906 in words is "one million, nine hundred ninety-one thousand, nine hundred six".