66673393781 has 2 divisors, whose sum is σ = 66673393782. Its totient is φ = 66673393780.

The previous prime is 66673393777. The next prime is 66673393799. The reversal of 66673393781 is 18739337666.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 62152983025 + 4520410756 = 249305^2 + 67234^2 .

It is a cyclic number.

It is not a de Polignac number, because 66673393781 - 2² = 66673393777 is a prime.

It is a super-2 number, since 2×66673393781² (a number of 22 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 66673393781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66673393751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33336696890 + 33336696891.

It is an arithmetic number, because the mean of its divisors is an integer number (33336696891).

Almost surely, 2^66673393781 is an apocalyptic number.

It is an amenable number.

66673393781 is a deficient number, since it is larger than the sum of its proper divisors (1).

66673393781 is an equidigital number, since it uses as much as digits as its factorization.

66673393781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20575296, while the sum is 59.

The spelling of 66673393781 in words is "sixty-six billion, six hundred seventy-three million, three hundred ninety-three thousand, seven hundred eighty-one".