671 has 4 divisors (see below), whose sum is σ = 744. Its totient is φ = 600.

The previous prime is 661. The next prime is 673. The reversal of 671 is 176.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 671 - 2⁶ = 607 is a prime.

It is a Duffinian number.

It is a plaindrome in base 8, base 12, base 14 and base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (673) 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, 20 + ... + 41.

It is an arithmetic number, because the mean of its divisors is an integer number (186).

It is the magic constant of a 11 × 11 magic square.

2⁶⁷¹ is an apocalyptic number.

671 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

671 is a deficient number, since it is larger than the sum of its proper divisors (73).

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

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

The sum of its prime factors is 72.

The product of its digits is 42, while the sum is 14.

The square root of 671 is about 25.9036676940. The cubic root of 671 is about 8.7546913618.

Multiplying 671 by its product of digits (42), we get a palindrome (28182).

It can be divided in two parts, 6 and 71, that added together give a palindrome (77).

The spelling of 671 in words is "six hundred seventy-one", and thus it is an aban number.