66500391 has 4 divisors (see below), whose sum is σ = 88667192. Its totient is φ = 44333592.

The previous prime is 66500389. The next prime is 66500407. The reversal of 66500391 is 19300566.

It is a happy number.

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

It is not a de Polignac number, because 66500391 - 2¹ = 66500389 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66500321) 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, 11083396 + ... + 11083401.

It is an arithmetic number, because the mean of its divisors is an integer number (22166798).

Almost surely, 2^66500391 is an apocalyptic number.

66500391 is a deficient number, since it is larger than the sum of its proper divisors (22166801).

66500391 is a wasteful number, since it uses less digits than its factorization.

66500391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22166800.

The product of its (nonzero) digits is 4860, while the sum is 30.

The square root of 66500391 is about 8154.7771888630. Note that the first 3 decimals coincide. The cubic root of 66500391 is about 405.1427449882.

The spelling of 66500391 in words is "sixty-six million, five hundred thousand, three hundred ninety-one".