66653659981 has 2 divisors, whose sum is σ = 66653659982. Its totient is φ = 66653659980.

The previous prime is 66653659957. The next prime is 66653660041. The reversal of 66653659981 is 18995635666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64838473956 + 1815186025 = 254634^2 + 42605^2 .

It is a cyclic number.

It is not a de Polignac number, because 66653659981 - 2²³ = 66645271373 is a prime.

It is a super-2 number, since 2×66653659981² (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 (66653659931) 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, 33326829990 + 33326829991.

It is an arithmetic number, because the mean of its divisors is an integer number (33326829991).

Almost surely, 2^66653659981 is an apocalyptic number.

It is an amenable number.

66653659981 is a deficient number, since it is larger than the sum of its proper divisors (1).

66653659981 is an equidigital number, since it uses as much as digits as its factorization.

66653659981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62985600, while the sum is 64.

The spelling of 66653659981 in words is "sixty-six billion, six hundred fifty-three million, six hundred fifty-nine thousand, nine hundred eighty-one".