671661 has 12 divisors (see below), whose sum is σ = 996892. Its totient is φ = 435456.

The previous prime is 671651. The next prime is 671681. The reversal of 671661 is 166176.

It can be written as a sum of positive squares in 2 ways, for example, as 585225 + 86436 = 765^2 + 294^2 .

It is not a de Polignac number, because 671661 - 2⁷ = 671533 is a prime.

It is a super-3 number, since 3×671661³ = 909016256141333343, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a plaindrome in base 14.

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 671661.

It is not an unprimeable number, because it can be changed into a prime (671651) 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 11 ways as a sum of consecutive naturals, for example, 676 + ... + 1341.

2⁶⁷¹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

671661 is a deficient number, since it is larger than the sum of its proper divisors (325231).

671661 is a wasteful number, since it uses less digits than its factorization.

671661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2060 (or 2057 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 671661 is about 819.5492663654. The cubic root of 671661 is about 87.5756515804.

It can be divided in two parts, 67 and 1661, that added together give a cube (1728 = 12³).

The spelling of 671661 in words is "six hundred seventy-one thousand, six hundred sixty-one".