66566391 has 4 divisors (see below), whose sum is σ = 88755192. Its totient is φ = 44377592.

The previous prime is 66566363. The next prime is 66566413. The reversal of 66566391 is 19366566.

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 66566391 - 2⁵ = 66566359 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66566321) 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, 11094396 + ... + 11094401.

It is an arithmetic number, because the mean of its divisors is an integer number (22188798).

Almost surely, 2^66566391 is an apocalyptic number.

66566391 is a deficient number, since it is larger than the sum of its proper divisors (22188801).

66566391 is a wasteful number, since it uses less digits than its factorization.

66566391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22188800.

The product of its digits is 174960, while the sum is 42.

The square root of 66566391 is about 8158.8228930404. The cubic root of 66566391 is about 405.2767320700.

The spelling of 66566391 in words is "sixty-six million, five hundred sixty-six thousand, three hundred ninety-one".