1800991 has 4 divisors (see below), whose sum is σ = 1895800. Its totient is φ = 1706184.

The previous prime is 1800979. The next prime is 1801003. The reversal of 1800991 is 1990081.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1800979) and next prime (1801003).

It is a cyclic number.

It is not a de Polignac number, because 1800991 - 2⁵ = 1800959 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1800961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47376 + ... + 47413.

It is an arithmetic number, because the mean of its divisors is an integer number (473950).

2^1800991 is an apocalyptic number.

1800991 is a deficient number, since it is larger than the sum of its proper divisors (94809).

1800991 is an equidigital number, since it uses as much as digits as its factorization.

1800991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94808.

The product of its (nonzero) digits is 648, while the sum is 28.

The square root of 1800991 is about 1342.0100595748. The cubic root of 1800991 is about 121.6663597499. Note that the first 3 decimals are identical.

The spelling of 1800991 in words is "one million, eight hundred thousand, nine hundred ninety-one".