66678261809 has 2 divisors, whose sum is σ = 66678261810. Its totient is φ = 66678261808.

The previous prime is 66678261791. The next prime is 66678261851. The reversal of 66678261809 is 90816287666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66549552784 + 128709025 = 257972^2 + 11345^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66678261809 is a prime.

It is not a weakly prime, because it can be changed into another prime (66278261809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33339130904 + 33339130905.

It is an arithmetic number, because the mean of its divisors is an integer number (33339130905).

Almost surely, 2^66678261809 is an apocalyptic number.

It is an amenable number.

66678261809 is a deficient number, since it is larger than the sum of its proper divisors (1).

66678261809 is an equidigital number, since it uses as much as digits as its factorization.

66678261809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10450944, while the sum is 59.

The spelling of 66678261809 in words is "sixty-six billion, six hundred seventy-eight million, two hundred sixty-one thousand, eight hundred nine".