66617381 has 2 divisors, whose sum is σ = 66617382. Its totient is φ = 66617380.

The previous prime is 66617371. The next prime is 66617387. The reversal of 66617381 is 18371666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 45832900 + 20784481 = 6770^2 + 4559^2 .

It is a cyclic number.

It is not a de Polignac number, because 66617381 - 2¹⁰ = 66616357 is a prime.

It is a super-2 number, since 2×66617381² = 8875750902598322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66617387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33308690 + 33308691.

It is an arithmetic number, because the mean of its divisors is an integer number (33308691).

Almost surely, 2^66617381 is an apocalyptic number.

It is an amenable number.

66617381 is a deficient number, since it is larger than the sum of its proper divisors (1).

66617381 is an equidigital number, since it uses as much as digits as its factorization.

66617381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 38.

The square root of 66617381 is about 8161.9471328844. The cubic root of 66617381 is about 405.3801866112.

The spelling of 66617381 in words is "sixty-six million, six hundred seventeen thousand, three hundred eighty-one".