664445581 has 2 divisors, whose sum is σ = 664445582. Its totient is φ = 664445580.

The previous prime is 664445563. The next prime is 664445603. The reversal of 664445581 is 185544466.

664445581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 661775625 + 2669956 = 25725^2 + 1634^2 .

It is a cyclic number.

It is not a de Polignac number, because 664445581 - 2¹⁷ = 664314509 is a prime.

It is a super-2 number, since 2×664445581² = 882975860220855122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664445381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332222790 + 332222791.

It is an arithmetic number, because the mean of its divisors is an integer number (332222791).

Almost surely, 2^664445581 is an apocalyptic number.

It is an amenable number.

664445581 is a deficient number, since it is larger than the sum of its proper divisors (1).

664445581 is an equidigital number, since it uses as much as digits as its factorization.

664445581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 460800, while the sum is 43.

The square root of 664445581 is about 25776.8419516433. The cubic root of 664445581 is about 872.6092368218.

It can be divided in two parts, 6644 and 45581, that added together give a palindrome (52225).

The spelling of 664445581 in words is "six hundred sixty-four million, four hundred forty-five thousand, five hundred eighty-one".