666761 has 4 divisors (see below), whose sum is σ = 676224. Its totient is φ = 657300.

The previous prime is 666751. The next prime is 666769. The reversal of 666761 is 167666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 167666 = 2 ⋅83833.

It is a cyclic number.

It is not a de Polignac number, because 666761 - 2⁶ = 666697 is a prime.

It is a super-2 number, since 2×666761² = 889140462242, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (666769) 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, 4625 + ... + 4766.

It is an arithmetic number, because the mean of its divisors is an integer number (169056).

2⁶⁶⁶⁷⁶¹ is an apocalyptic number.

It is an amenable number.

666761 is a deficient number, since it is larger than the sum of its proper divisors (9463).

666761 is an equidigital number, since it uses as much as digits as its factorization.

666761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9462.

The product of its digits is 9072, while the sum is 32.

The square root of 666761 is about 816.5543460175. The cubic root of 666761 is about 87.3621666672.

The spelling of 666761 in words is "six hundred sixty-six thousand, seven hundred sixty-one".