66721841 has 4 divisors (see below), whose sum is σ = 68525172. Its totient is φ = 64918512.

The previous prime is 66721829. The next prime is 66721847. The reversal of 66721841 is 14812766.

66721841 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 14812766 = 2 ⋅7406383.

It can be written as a sum of positive squares in 2 ways, for example, as 30481441 + 36240400 = 5521^2 + 6020^2 .

It is a cyclic number.

It is not a de Polignac number, because 66721841 - 2⁶ = 66721777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66721847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 901610 + ... + 901683.

It is an arithmetic number, because the mean of its divisors is an integer number (17131293).

Almost surely, 2^66721841 is an apocalyptic number.

It is an amenable number.

66721841 is a deficient number, since it is larger than the sum of its proper divisors (1803331).

66721841 is a wasteful number, since it uses less digits than its factorization.

66721841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1803330.

The product of its digits is 16128, while the sum is 35.

The square root of 66721841 is about 8168.3438345848. The cubic root of 66721841 is about 405.5919626734.

The spelling of 66721841 in words is "sixty-six million, seven hundred twenty-one thousand, eight hundred forty-one".