66855865 has 4 divisors (see below), whose sum is σ = 80227044. Its totient is φ = 53484688.

The previous prime is 66855827. The next prime is 66855881. The reversal of 66855865 is 56855866.

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 13682601 + 53173264 = 3699^2 + 7292^2 .

It is a cyclic number.

It is not a de Polignac number, because 66855865 - 2¹¹ = 66853817 is a prime.

It is a Duffinian 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, 6685582 + ... + 6685591.

It is an arithmetic number, because the mean of its divisors is an integer number (20056761).

Almost surely, 2^66855865 is an apocalyptic number.

It is an amenable number.

66855865 is a deficient number, since it is larger than the sum of its proper divisors (13371179).

66855865 is a wasteful number, since it uses less digits than its factorization.

66855865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13371178.

The product of its digits is 1728000, while the sum is 49.

The square root of 66855865 is about 8176.5435851587. The cubic root of 66855865 is about 405.8633515718.

Subtracting from 66855865 its reverse (56855866), we obtain a palindrome (9999999).

The spelling of 66855865 in words is "sixty-six million, eight hundred fifty-five thousand, eight hundred sixty-five".