66749581 has 2 divisors, whose sum is σ = 66749582. Its totient is φ = 66749580.

The previous prime is 66749569. The next prime is 66749647. The reversal of 66749581 is 18594766.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 38564100 + 28185481 = 6210^2 + 5309^2 .

It is a cyclic number.

It is not a de Polignac number, because 66749581 - 2¹¹ = 66747533 is a prime.

It is a super-2 number, since 2×66749581² = 8911013127351122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66749281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33374790 + 33374791.

It is an arithmetic number, because the mean of its divisors is an integer number (33374791).

Almost surely, 2^66749581 is an apocalyptic number.

It is an amenable number.

66749581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66749581 is an equidigital number, since it uses as much as digits as its factorization.

66749581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362880, while the sum is 46.

The square root of 66749581 is about 8170.0416767603. The cubic root of 66749581 is about 405.6481639712.

The spelling of 66749581 in words is "sixty-six million, seven hundred forty-nine thousand, five hundred eighty-one".