66081581 has 2 divisors, whose sum is σ = 66081582. Its totient is φ = 66081580.

The previous prime is 66081569. The next prime is 66081611. The reversal of 66081581 is 18518066.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64722025 + 1359556 = 8045^2 + 1166^2 .

It is a cyclic number.

It is not a de Polignac number, because 66081581 - 2¹⁸ = 65819437 is a prime.

It is a super-3 number, since 3×66081581³ (a number of 24 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66081511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33040790 + 33040791.

It is an arithmetic number, because the mean of its divisors is an integer number (33040791).

Almost surely, 2^66081581 is an apocalyptic number.

It is an amenable number.

66081581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66081581 is an equidigital number, since it uses as much as digits as its factorization.

66081581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 66081581 is about 8129.0578174841. The cubic root of 66081581 is about 404.2904427973.

The spelling of 66081581 in words is "sixty-six million, eighty-one thousand, five hundred eighty-one".