665566557 has 4 divisors (see below), whose sum is σ = 887422080. Its totient is φ = 443711036.

The previous prime is 665566537. The next prime is 665566607. The reversal of 665566557 is 755665566.

It is a happy number.

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.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665566557 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665566537) 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, 110927757 + ... + 110927762.

It is an arithmetic number, because the mean of its divisors is an integer number (221855520).

Almost surely, 2^665566557 is an apocalyptic number.

It is an amenable number.

665566557 is a deficient number, since it is larger than the sum of its proper divisors (221855523).

665566557 is a wasteful number, since it uses less digits than its factorization.

665566557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221855522.

The product of its digits is 5670000, while the sum is 51.

The square root of 665566557 is about 25798.5766467842. The cubic root of 665566557 is about 873.0996830260.

Subtracting 665566557 from its reverse (755665566), we obtain a palindrome (90099009).

The spelling of 665566557 in words is "six hundred sixty-five million, five hundred sixty-six thousand, five hundred fifty-seven".