66800721 has 8 divisors (see below), whose sum is σ = 95919040. Its totient is φ = 41108112.

The previous prime is 66800711. The next prime is 66800729. The reversal of 66800721 is 12700866.

It is a happy number.

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

It is not a de Polignac number, because 66800721 - 2⁵ = 66800689 is a prime.

It is a super-2 number, since 2×66800721² = 8924672652239682, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66800729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 856381 + ... + 856458.

It is an arithmetic number, because the mean of its divisors is an integer number (11989880).

Almost surely, 2^66800721 is an apocalyptic number.

It is an amenable number.

66800721 is a deficient number, since it is larger than the sum of its proper divisors (29118319).

66800721 is a wasteful number, since it uses less digits than its factorization.

66800721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1712855.

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 66800721 is about 8173.1708045287. The cubic root of 66800721 is about 405.7517329184.

The spelling of 66800721 in words is "sixty-six million, eight hundred thousand, seven hundred twenty-one".