66442690406781 has 24 divisors (see below), whose sum is σ = 103392354887640. Its totient is φ = 40873148896896.

The previous prime is 66442690406779. The next prime is 66442690406821. The reversal of 66442690406781 is 18760409624466.

It is a happy number.

66442690406781 is a `hidden beast` number, since 6 + 6 + 4 + 426 + 90 + 40 + 6 + 7 + 81 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 13902532532100 + 52540157874681 = 3728610^2 + 7248459^2 .

It is not a de Polignac number, because 66442690406781 - 2¹ = 66442690406779 is a prime.

It is a super-2 number, since 2×66442690406781² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66442690404781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 101481906 + ... + 102134531.

It is an arithmetic number, because the mean of its divisors is an integer number (4308014786985).

Almost surely, 2^{66442690406781} is an apocalyptic number.

It is an amenable number.

66442690406781 is a deficient number, since it is larger than the sum of its proper divisors (36949664480859).

66442690406781 is a wasteful number, since it uses less digits than its factorization.

66442690406781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203619245 (or 203619242 counting only the distinct ones).

The product of its (nonzero) digits is 83607552, while the sum is 63.

The spelling of 66442690406781 in words is "sixty-six trillion, four hundred forty-two billion, six hundred ninety million, four hundred six thousand, seven hundred eighty-one".