66113997581 has 2 divisors, whose sum is σ = 66113997582. Its totient is φ = 66113997580.

The previous prime is 66113997533. The next prime is 66113997617. The reversal of 66113997581 is 18579931166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62437515625 + 3676481956 = 249875^2 + 60634^2 .

It is a cyclic number.

It is not a de Polignac number, because 66113997581 - 2⁶ = 66113997517 is a prime.

It is a super-2 number, since 2×66113997581² (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 (66113997181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33056998790 + 33056998791.

It is an arithmetic number, because the mean of its divisors is an integer number (33056998791).

Almost surely, 2^66113997581 is an apocalyptic number.

It is an amenable number.

66113997581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66113997581 is an equidigital number, since it uses as much as digits as its factorization.

66113997581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2449440, while the sum is 56.

The spelling of 66113997581 in words is "sixty-six billion, one hundred thirteen million, nine hundred ninety-seven thousand, five hundred eighty-one".