66640191 has 4 divisors (see below), whose sum is σ = 88853592. Its totient is φ = 44426792.

The previous prime is 66640159. The next prime is 66640199. The reversal of 66640191 is 19104666.

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 66640191 - 2⁵ = 66640159 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66640199) 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, 11106696 + ... + 11106701.

It is an arithmetic number, because the mean of its divisors is an integer number (22213398).

Almost surely, 2^66640191 is an apocalyptic number.

66640191 is a deficient number, since it is larger than the sum of its proper divisors (22213401).

66640191 is a wasteful number, since it uses less digits than its factorization.

66640191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22213400.

The product of its (nonzero) digits is 7776, while the sum is 33.

The square root of 66640191 is about 8163.3443514285. The cubic root of 66640191 is about 405.4264491468.

The spelling of 66640191 in words is "sixty-six million, six hundred forty thousand, one hundred ninety-one".