1981791 has 24 divisors (see below), whose sum is σ = 3319680. Its totient is φ = 1115856.

The previous prime is 1981787. The next prime is 1981813. The reversal of 1981791 is 1971891.

It is not a de Polignac number, because 1981791 - 2² = 1981787 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981711) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5040 + ... + 5418.

It is an arithmetic number, because the mean of its divisors is an integer number (138320).

2^1981791 is an apocalyptic number.

1981791 is a deficient number, since it is larger than the sum of its proper divisors (1337889).

1981791 is a wasteful number, since it uses less digits than its factorization.

1981791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475 (or 472 counting only the distinct ones).

The product of its digits is 4536, while the sum is 36.

The square root of 1981791 is about 1407.7609882363. The cubic root of 1981791 is about 125.6085736301.

It can be divided in two parts, 1981 and 791, that added together give a palindrome (2772).

The spelling of 1981791 in words is "one million, nine hundred eighty-one thousand, seven hundred ninety-one".