1221665377 has 2 divisors, whose sum is σ = 1221665378. Its totient is φ = 1221665376.

The previous prime is 1221665369. The next prime is 1221665381. The reversal of 1221665377 is 7735661221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 678029521 + 543635856 = 26039^2 + 23316^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221665377 - 2³ = 1221665369 is a prime.

It is not a weakly prime, because it can be changed into another prime (1221669377) 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, 610832688 + 610832689.

It is an arithmetic number, because the mean of its divisors is an integer number (610832689).

Almost surely, 2^1221665377 is an apocalyptic number.

It is an amenable number.

1221665377 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221665377 is an equidigital number, since it uses as much as digits as its factorization.

1221665377 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 105840, while the sum is 40.

The square root of 1221665377 is about 34952.3300653905. The cubic root of 1221665377 is about 1069.0157125909.

The spelling of 1221665377 in words is "one billion, two hundred twenty-one million, six hundred sixty-five thousand, three hundred seventy-seven".