66688999 has 16 divisors (see below), whose sum is σ = 73773504. Its totient is φ = 59904000.

The previous prime is 66688991. The next prime is 66689017. The reversal of 66688999 is 99988666.

It is not a de Polignac number, because 66688999 - 2³ = 66688991 is a prime.

66688999 is a strobogrammatic number because it is the same when read upside-down.

It is a Duffinian number.

It is a plaindrome in base 10.

It is a zygodrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66688991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 103719 + ... + 104359.

It is an arithmetic number, because the mean of its divisors is an integer number (4610844).

Almost surely, 2^66688999 is an apocalyptic number.

66688999 is a deficient number, since it is larger than the sum of its proper divisors (7084505).

66688999 is a wasteful number, since it uses less digits than its factorization.

66688999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 858.

The product of its digits is 10077696, while the sum is 61.

The square root of 66688999 is about 8166.3332653033. Note that the first 3 decimals coincide. The cubic root of 66688999 is about 405.5254045710.

The spelling of 66688999 in words is "sixty-six million, six hundred eighty-eight thousand, nine hundred ninety-nine".