66681339509 has 2 divisors, whose sum is σ = 66681339510. Its totient is φ = 66681339508.

The previous prime is 66681339503. The next prime is 66681339521. The reversal of 66681339509 is 90593318666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66575352484 + 105987025 = 258022^2 + 10295^2 .

It is a cyclic number.

It is not a de Polignac number, because 66681339509 - 2¹⁶ = 66681273973 is a prime.

It is a super-2 number, since 2×66681339509² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66681339503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33340669754 + 33340669755.

It is an arithmetic number, because the mean of its divisors is an integer number (33340669755).

Almost surely, 2^66681339509 is an apocalyptic number.

It is an amenable number.

66681339509 is a deficient number, since it is larger than the sum of its proper divisors (1).

66681339509 is an equidigital number, since it uses as much as digits as its factorization.

66681339509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6298560, while the sum is 56.

The spelling of 66681339509 in words is "sixty-six billion, six hundred eighty-one million, three hundred thirty-nine thousand, five hundred nine".