665550591 has 4 divisors (see below), whose sum is σ = 887400792. Its totient is φ = 443700392.

The previous prime is 665550583. The next prime is 665550617. The reversal of 665550591 is 195055566.

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

It is a cyclic number.

It is not a de Polignac number, because 665550591 - 2³ = 665550583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665550541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110925096 + ... + 110925101.

It is an arithmetic number, because the mean of its divisors is an integer number (221850198).

Almost surely, 2^665550591 is an apocalyptic number.

665550591 is a deficient number, since it is larger than the sum of its proper divisors (221850201).

665550591 is a wasteful number, since it uses less digits than its factorization.

665550591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221850200.

The product of its (nonzero) digits is 202500, while the sum is 42.

The square root of 665550591 is about 25798.2672092526. The cubic root of 665550591 is about 873.0927014948.

The spelling of 665550591 in words is "six hundred sixty-five million, five hundred fifty thousand, five hundred ninety-one".