665005381 has 2 divisors, whose sum is σ = 665005382. Its totient is φ = 665005380.

The previous prime is 665005361. The next prime is 665005427. The reversal of 665005381 is 183500566.

665005381 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., 335256100 + 329749281 = 18310^2 + 18159^2 .

It is a cyclic number.

It is not a de Polignac number, because 665005381 - 2¹⁵ = 664972613 is a prime.

It is a super-2 number, since 2×665005381² = 884464313517910322, which contains 22 as substring.

It is equal to p_34532593 and since 665005381 and 34532593 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665005361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332502690 + 332502691.

It is an arithmetic number, because the mean of its divisors is an integer number (332502691).

Almost surely, 2^665005381 is an apocalyptic number.

It is an amenable number.

665005381 is a deficient number, since it is larger than the sum of its proper divisors (1).

665005381 is an equidigital number, since it uses as much as digits as its factorization.

665005381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 665005381 is about 25787.6982493591. The cubic root of 665005381 is about 872.8542278060.

The spelling of 665005381 in words is "six hundred sixty-five million, five thousand, three hundred eighty-one".