671721 has 8 divisors (see below), whose sum is σ = 948384. Its totient is φ = 421440.

The previous prime is 671717. The next prime is 671729. The reversal of 671721 is 127176.

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

It is not a de Polignac number, because 671721 - 2² = 671717 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 671691 and 671700.

It is not an unprimeable number, because it can be changed into a prime (671729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6535 + ... + 6636.

It is an arithmetic number, because the mean of its divisors is an integer number (118548).

2⁶⁷¹⁷²¹ is an apocalyptic number.

It is an amenable number.

671721 is a deficient number, since it is larger than the sum of its proper divisors (276663).

671721 is a wasteful number, since it uses less digits than its factorization.

671721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13191.

The product of its digits is 588, while the sum is 24.

The square root of 671721 is about 819.5858710349. The cubic root of 671721 is about 87.5782592365.

Adding to 671721 its reverse (127176), we get a palindrome (798897).

The spelling of 671721 in words is "six hundred seventy-one thousand, seven hundred twenty-one".