1261666321 has 2 divisors, whose sum is σ = 1261666322. Its totient is φ = 1261666320.

The previous prime is 1261666313. The next prime is 1261666327. The reversal of 1261666321 is 1236661621.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 947100625 + 314565696 = 30775^2 + 17736^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261666321 - 2³ = 1261666313 is a prime.

It is not a weakly prime, because it can be changed into another prime (1261666327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630833160 + 630833161.

It is an arithmetic number, because the mean of its divisors is an integer number (630833161).

Almost surely, 2^1261666321 is an apocalyptic number.

It is an amenable number.

1261666321 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261666321 is an equidigital number, since it uses as much as digits as its factorization.

1261666321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 34.

The square root of 1261666321 is about 35519.9425815977. The cubic root of 1261666321 is about 1080.5582165134.

The spelling of 1261666321 in words is "one billion, two hundred sixty-one million, six hundred sixty-six thousand, three hundred twenty-one".