660861 has 12 divisors (see below), whose sum is σ = 965692. Its totient is φ = 435456.

The previous prime is 660853. The next prime is 660887. The reversal of 660861 is 168066.

It can be written as a sum of positive squares in 2 ways, for example, as 352836 + 308025 = 594^2 + 555^2 .

It is not a de Polignac number, because 660861 - 2³ = 660853 is a prime.

It is a super-2 number, since 2×660861² = 873474522642, which contains 22 as substring.

It is a Duffinian number.

660861 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 495 + ... + 1251.

2⁶⁶⁰⁸⁶¹ is an apocalyptic number.

It is an amenable number.

660861 is a deficient number, since it is larger than the sum of its proper divisors (304831).

660861 is a wasteful number, since it uses less digits than its factorization.

660861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860 (or 857 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 660861 is about 812.9335766223. The cubic root of 660861 is about 87.1037209247.

It can be divided in two parts, 660 and 861, that added together give a square (1521 = 39²).

The spelling of 660861 in words is "six hundred sixty thousand, eight hundred sixty-one".