66561998 has 8 divisors (see below), whose sum is σ = 100572192. Its totient is φ = 33037936.

The previous prime is 66561973. The next prime is 66562019. The reversal of 66561998 is 89916566.

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

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 121190 + ... + 121737.

It is an arithmetic number, because the mean of its divisors is an integer number (12571524).

Almost surely, 2^66561998 is an apocalyptic number.

66561998 is a deficient number, since it is larger than the sum of its proper divisors (34010194).

66561998 is a wasteful number, since it uses less digits than its factorization.

66561998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243066.

The product of its digits is 699840, while the sum is 50.

The square root of 66561998 is about 8158.5536708414. The cubic root of 66561998 is about 405.2678165606.

The spelling of 66561998 in words is "sixty-six million, five hundred sixty-one thousand, nine hundred ninety-eight".