66780358205581 has 2 divisors, whose sum is σ = 66780358205582. Its totient is φ = 66780358205580.

The previous prime is 66780358205531. The next prime is 66780358205647. The reversal of 66780358205581 is 18550285308766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 48258447048900 + 18521911156681 = 6946830^2 + 4303709^2 .

It is a cyclic number.

It is not a de Polignac number, because 66780358205581 - 2⁷ = 66780358205453 is a prime.

It is a super-2 number, since 2×66780358205581² (a number of 28 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66780358205531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33390179102790 + 33390179102791.

It is an arithmetic number, because the mean of its divisors is an integer number (33390179102791).

Almost surely, 2^{66780358205581} is an apocalyptic number.

It is an amenable number.

66780358205581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66780358205581 is an equidigital number, since it uses as much as digits as its factorization.

66780358205581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96768000, while the sum is 64.

The spelling of 66780358205581 in words is "sixty-six trillion, seven hundred eighty billion, three hundred fifty-eight million, two hundred five thousand, five hundred eighty-one".