66780055621601 has 16 divisors (see below), whose sum is σ = 76410007584768. Its totient is φ = 57172629200400.

The previous prime is 66780055621579. The next prime is 66780055621729. The reversal of 66780055621601 is 10612655008766.

It is a happy number.

It is not a de Polignac number, because 66780055621601 - 2³⁰ = 66778981879777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66780055621901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18643616 + ... + 21935006.

It is an arithmetic number, because the mean of its divisors is an integer number (4775625474048).

Almost surely, 2^{66780055621601} is an apocalyptic number.

It is an amenable number.

66780055621601 is a deficient number, since it is larger than the sum of its proper divisors (9629951963167).

66780055621601 is a wasteful number, since it uses less digits than its factorization.

66780055621601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3294812.

The product of its (nonzero) digits is 3628800, while the sum is 53.

The spelling of 66780055621601 in words is "sixty-six trillion, seven hundred eighty billion, fifty-five million, six hundred twenty-one thousand, six hundred one".