66681339961 has 2 divisors, whose sum is σ = 66681339962. Its totient is φ = 66681339960.

The previous prime is 66681339941. The next prime is 66681340021. The reversal of 66681339961 is 16993318666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 45469165225 + 21212174736 = 213235^2 + 145644^2 .

It is a cyclic number.

It is not a de Polignac number, because 66681339961 - 2⁹ = 66681339449 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 66681339896 and 66681339905.

It is not a weakly prime, because it can be changed into another prime (66681339931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33340669980 + 33340669981.

It is an arithmetic number, because the mean of its divisors is an integer number (33340669981).

Almost surely, 2^66681339961 is an apocalyptic number.

It is an amenable number.

66681339961 is a deficient number, since it is larger than the sum of its proper divisors (1).

66681339961 is an equidigital number, since it uses as much as digits as its factorization.

66681339961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7558272, while the sum is 58.

The spelling of 66681339961 in words is "sixty-six billion, six hundred eighty-one million, three hundred thirty-nine thousand, nine hundred sixty-one".