666961 has 4 divisors (see below), whose sum is σ = 706212. Its totient is φ = 627712.

The previous prime is 666959. The next prime is 666979. The reversal of 666961 is 169666.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 231361 + 435600 = 481^2 + 660^2 .

It is a cyclic number.

It is not a de Polignac number, because 666961 - 2¹ = 666959 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19600 + ... + 19633.

It is an arithmetic number, because the mean of its divisors is an integer number (176553).

2⁶⁶⁶⁹⁶¹ is an apocalyptic number.

It is an amenable number.

666961 is a deficient number, since it is larger than the sum of its proper divisors (39251).

666961 is a wasteful number, since it uses less digits than its factorization.

666961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39250.

The product of its digits is 11664, while the sum is 34.

The square root of 666961 is about 816.6768026582. The cubic root of 666961 is about 87.3709007746.

The spelling of 666961 in words is "six hundred sixty-six thousand, nine hundred sixty-one".