66719581 has 2 divisors, whose sum is σ = 66719582. Its totient is φ = 66719580.

The previous prime is 66719579. The next prime is 66719647. The reversal of 66719581 is 18591766.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 39062500 + 27657081 = 6250^2 + 5259^2 .

It is a cyclic number.

It is not a de Polignac number, because 66719581 - 2¹ = 66719579 is a prime.

It is a super-2 number, since 2×66719581² = 8903004977631122, which contains 22 as substring.

Together with 66719579, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66719551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33359790 + 33359791.

It is an arithmetic number, because the mean of its divisors is an integer number (33359791).

Almost surely, 2^66719581 is an apocalyptic number.

It is an amenable number.

66719581 is a deficient number, since it is larger than the sum of its proper divisors (1).

66719581 is an equidigital number, since it uses as much as digits as its factorization.

66719581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 43.

The square root of 66719581 is about 8168.2054944767. The cubic root of 66719581 is about 405.5873832225.

The spelling of 66719581 in words is "sixty-six million, seven hundred nineteen thousand, five hundred eighty-one".