664445381 has 2 divisors, whose sum is σ = 664445382. Its totient is φ = 664445380.

The previous prime is 664445363. The next prime is 664445393. The reversal of 664445381 is 183544466.

It is a happy number.

664445381 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 477029281 + 187416100 = 21841^2 + 13690^2 .

It is a cyclic number.

It is not a de Polignac number, because 664445381 - 2¹⁴ = 664428997 is a prime.

It is a super-3 number, since 3×664445381³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (664445581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332222690 + 332222691.

It is an arithmetic number, because the mean of its divisors is an integer number (332222691).

Almost surely, 2^664445381 is an apocalyptic number.

It is an amenable number.

664445381 is a deficient number, since it is larger than the sum of its proper divisors (1).

664445381 is an equidigital number, since it uses as much as digits as its factorization.

664445381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 276480, while the sum is 41.

The square root of 664445381 is about 25776.8380721919. The cubic root of 664445381 is about 872.6091492691.

It can be divided in two parts, 6644 and 45381, that added together give a palindrome (52025).

The spelling of 664445381 in words is "six hundred sixty-four million, four hundred forty-five thousand, three hundred eighty-one".