665154221 has 2 divisors, whose sum is σ = 665154222. Its totient is φ = 665154220.

The previous prime is 665154169. The next prime is 665154239. The reversal of 665154221 is 122451566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 365344996 + 299809225 = 19114^2 + 17315^2 .

It is a cyclic number.

It is not a de Polignac number, because 665154221 - 2⁶ = 665154157 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (665154251) 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, 332577110 + 332577111.

It is an arithmetic number, because the mean of its divisors is an integer number (332577111).

Almost surely, 2^665154221 is an apocalyptic number.

It is an amenable number.

665154221 is a deficient number, since it is larger than the sum of its proper divisors (1).

665154221 is an equidigital number, since it uses as much as digits as its factorization.

665154221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14400, while the sum is 32.

The square root of 665154221 is about 25790.5839600425. The cubic root of 665154221 is about 872.9193430344.

The spelling of 665154221 in words is "six hundred sixty-five million, one hundred fifty-four thousand, two hundred twenty-one".