66555565 has 4 divisors (see below), whose sum is σ = 79866684. Its totient is φ = 53244448.

The previous prime is 66555553. The next prime is 66555581. The reversal of 66555565 is 56555566.

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 23561316 + 42994249 = 4854^2 + 6557^2 .

It is a cyclic number.

It is not a de Polignac number, because 66555565 - 2¹¹ = 66553517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6655552 + ... + 6655561.

It is an arithmetic number, because the mean of its divisors is an integer number (19966671).

Almost surely, 2^66555565 is an apocalyptic number.

It is an amenable number.

66555565 is a deficient number, since it is larger than the sum of its proper divisors (13311119).

66555565 is a wasteful number, since it uses less digits than its factorization.

66555565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13311118.

The product of its digits is 675000, while the sum is 43.

The square root of 66555565 is about 8158.1594125146. The cubic root of 66555565 is about 405.2547602024.

Subtracting from 66555565 its reverse (56555566), we obtain a palindrome (9999999).

The spelling of 66555565 in words is "sixty-six million, five hundred fifty-five thousand, five hundred sixty-five".