491681 has 4 divisors (see below), whose sum is σ = 501012. Its totient is φ = 482352.

The previous prime is 491677. The next prime is 491707. The reversal of 491681 is 186194.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 186194 = 2 ⋅93097.

It can be written as a sum of positive squares in 2 ways, for example, as 379456 + 112225 = 616^2 + 335^2 .

It is a cyclic number.

It is not a de Polignac number, because 491681 - 2² = 491677 is a prime.

It is a super-2 number, since 2×491681² = 483500411522, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 491681.

It is not an unprimeable number, because it can be changed into a prime (491611) 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, 4586 + ... + 4691.

It is an arithmetic number, because the mean of its divisors is an integer number (125253).

2⁴⁹¹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

491681 is a deficient number, since it is larger than the sum of its proper divisors (9331).

491681 is an equidigital number, since it uses as much as digits as its factorization.

491681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9330.

The product of its digits is 1728, while the sum is 29.

The square root of 491681 is about 701.1996862521. The cubic root of 491681 is about 78.9274021945.

It can be divided in two parts, 49 and 1681, that multiplied together give a square (82369 = 287²).

The spelling of 491681 in words is "four hundred ninety-one thousand, six hundred eighty-one".