1991273 has 4 divisors (see below), whose sum is σ = 1997268. Its totient is φ = 1985280.

The previous prime is 1991267. The next prime is 1991279. The reversal of 1991273 is 3721991.

It is a happy number.

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 (1991267) and next prime (1991279).

It can be written as a sum of positive squares in 2 ways, for example, as 1545049 + 446224 = 1243^2 + 668^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991273 - 2¹⁰ = 1990249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991279) 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 3 ways as a sum of consecutive naturals, for example, 2468 + ... + 3173.

It is an arithmetic number, because the mean of its divisors is an integer number (499317).

2^1991273 is an apocalyptic number.

It is an amenable number.

1991273 is a deficient number, since it is larger than the sum of its proper divisors (5995).

1991273 is an equidigital number, since it uses as much as digits as its factorization.

1991273 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5994.

The product of its digits is 3402, while the sum is 32.

The square root of 1991273 is about 1411.1247287182. The cubic root of 1991273 is about 125.8085822796.

The spelling of 1991273 in words is "one million, nine hundred ninety-one thousand, two hundred seventy-three".