66691447 has 4 divisors (see below), whose sum is σ = 68842816. Its totient is φ = 64540080.

The previous prime is 66691439. The next prime is 66691451. The reversal of 66691447 is 74419666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74419666 = 2 ⋅37209833.

It is a cyclic number.

It is not a de Polignac number, because 66691447 - 2³ = 66691439 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66691747) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1075638 + ... + 1075699.

It is an arithmetic number, because the mean of its divisors is an integer number (17210704).

Almost surely, 2^66691447 is an apocalyptic number.

66691447 is a deficient number, since it is larger than the sum of its proper divisors (2151369).

66691447 is a wasteful number, since it uses less digits than its factorization.

66691447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2151368.

The product of its digits is 217728, while the sum is 43.

The square root of 66691447 is about 8166.4831475979. The cubic root of 66691447 is about 405.5303664790.

The spelling of 66691447 in words is "sixty-six million, six hundred ninety-one thousand, four hundred forty-seven".