1991830 has 16 divisors (see below), whose sum is σ = 3601440. Its totient is φ = 793152.

The previous prime is 1991819. The next prime is 1991837. The reversal of 1991830 is 381991.

It is a junction number, because it is equal to n+sod(n) for n = 1991792 and 1991801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991837) by changing a digit.

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, 3847 + ... + 4333.

It is an arithmetic number, because the mean of its divisors is an integer number (225090).

2^1991830 is an apocalyptic number.

1991830 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1991830 is a deficient number, since it is larger than the sum of its proper divisors (1609610).

1991830 is a wasteful number, since it uses less digits than its factorization.

1991830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 903.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 1991830 is about 1411.3220752188. The cubic root of 1991830 is about 125.8203116017.

The spelling of 1991830 in words is "one million, nine hundred ninety-one thousand, eight hundred thirty".