491781 has 4 divisors (see below), whose sum is σ = 655712. Its totient is φ = 327852.

The previous prime is 491773. The next prime is 491783. The reversal of 491781 is 187194.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 491781 - 2³ = 491773 is a prime.

It is a super-2 number, since 2×491781² = 483697103922, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

491781 is a lucky number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 491781.

It is not an unprimeable number, because it can be changed into a prime (491783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 81961 + ... + 81966.

It is an arithmetic number, because the mean of its divisors is an integer number (163928).

2⁴⁹¹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

491781 is a deficient number, since it is larger than the sum of its proper divisors (163931).

491781 is a wasteful number, since it uses less digits than its factorization.

491781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163930.

The product of its digits is 2016, while the sum is 30.

The square root of 491781 is about 701.2709889907. The cubic root of 491781 is about 78.9327526861.

It can be divided in two parts, 49 and 1781, that added together give a triangular number (1830 = T₆₀).

The spelling of 491781 in words is "four hundred ninety-one thousand, seven hundred eighty-one".