66439999 has 8 divisors (see below), whose sum is σ = 68160960. Its totient is φ = 64731936.

The previous prime is 66439981. The next prime is 66440009. The reversal of 66439999 is 99993466.

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 66439999 - 2⁷ = 66439871 is a prime.

It is a Duffinian number.

66439999 is a modest number, since divided by 9999 gives 6643 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66439199) 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 7 ways as a sum of consecutive naturals, for example, 7677 + ... + 13849.

It is an arithmetic number, because the mean of its divisors is an integer number (8520120).

Almost surely, 2^66439999 is an apocalyptic number.

66439999 is a deficient number, since it is larger than the sum of its proper divisors (1720961).

66439999 is a wasteful number, since it uses less digits than its factorization.

66439999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6449.

The product of its digits is 2834352, while the sum is 55.

The square root of 66439999 is about 8151.0734875843. The cubic root of 66439999 is about 405.0200650527.

The spelling of 66439999 in words is "sixty-six million, four hundred thirty-nine thousand, nine hundred ninety-nine".