66388609 has 8 divisors (see below), whose sum is σ = 76912640. Its totient is φ = 56124576.

The previous prime is 66388561. The next prime is 66388657. The reversal of 66388609 is 90688366.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66388561) and next prime (66388657).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66388609 - 2⁷ = 66388481 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66388909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 64449 + ... + 65470.

It is an arithmetic number, because the mean of its divisors is an integer number (9614080).

Almost surely, 2^66388609 is an apocalyptic number.

It is an amenable number.

66388609 is a deficient number, since it is larger than the sum of its proper divisors (10524031).

66388609 is a wasteful number, since it uses less digits than its factorization.

66388609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129999.

The product of its (nonzero) digits is 373248, while the sum is 46.

The square root of 66388609 is about 8147.9205322585. The cubic root of 66388609 is about 404.9156131655.

The spelling of 66388609 in words is "sixty-six million, three hundred eighty-eight thousand, six hundred nine".