665909566 has 16 divisors (see below), whose sum is σ = 1142787456. Its totient is φ = 285082776.

The previous prime is 665909557. The next prime is 665909591.

It is a happy number.

665909566 is nontrivially palindromic in base 10.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11856 + ... + 38371.

It is an arithmetic number, because the mean of its divisors is an integer number (71424216).

Almost surely, 2^665909566 is an apocalyptic number.

665909566 is a deficient number, since it is larger than the sum of its proper divisors (476877890).

665909566 is a wasteful number, since it uses less digits than its factorization.

665909566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51183.

The product of its (nonzero) digits is 2624400, while the sum is 52.

The square root of 665909566 is about 25805.2236184847. The cubic root of 665909566 is about 873.2496452967.

The spelling of 665909566 in words is "six hundred sixty-five million, nine hundred nine thousand, five hundred sixty-six".