491721 has 8 divisors (see below), whose sum is σ = 666624. Its totient is φ = 322320.

The previous prime is 491719. The next prime is 491731. The reversal of 491721 is 127194.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 491721 - 2¹ = 491719 is a prime.

It is a Curzon number.

491721 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 491691 and 491700.

It is not an unprimeable number, because it can be changed into a prime (491731) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1161 + ... + 1526.

It is an arithmetic number, because the mean of its divisors is an integer number (83328).

2⁴⁹¹⁷²¹ is an apocalyptic number.

It is an amenable number.

491721 is a deficient number, since it is larger than the sum of its proper divisors (174903).

491721 is a wasteful number, since it uses less digits than its factorization.

491721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2751.

The product of its digits is 504, while the sum is 24.

The square root of 491721 is about 701.2282082176. The cubic root of 491721 is about 78.9295424782.

It can be divided in two parts, 49 and 1721, that added together give a triangular number (1770 = T₅₉).

The spelling of 491721 in words is "four hundred ninety-one thousand, seven hundred twenty-one".