66747581 has 2 divisors, whose sum is σ = 66747582. Its totient is φ = 66747580.

The previous prime is 66747547. The next prime is 66747599. The reversal of 66747581 is 18574766.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 41396356 + 25351225 = 6434^2 + 5035^2 .

It is a cyclic number.

It is not a de Polignac number, because 66747581 - 2¹⁸ = 66485437 is a prime.

It is a super-2 number, since 2×66747581² = 8910479138703122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66747181) 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, 33373790 + 33373791.

It is an arithmetic number, because the mean of its divisors is an integer number (33373791).

Almost surely, 2^66747581 is an apocalyptic number.

It is an amenable number.

66747581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66747581 is an equidigital number, since it uses as much as digits as its factorization.

66747581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 282240, while the sum is 44.

The square root of 66747581 is about 8169.9192774470. The cubic root of 66747581 is about 405.6441124879.

The spelling of 66747581 in words is "sixty-six million, seven hundred forty-seven thousand, five hundred eighty-one".