1221665369 has 2 divisors, whose sum is σ = 1221665370. Its totient is φ = 1221665368.

The previous prime is 1221665299. The next prime is 1221665377. The reversal of 1221665369 is 9635661221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1118032969 + 103632400 = 33437^2 + 10180^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221665369 - 2⁸ = 1221665113 is a prime.

It is a super-2 number, since 2×1221665369² = 2984932547627812322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1221665869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610832684 + 610832685.

It is an arithmetic number, because the mean of its divisors is an integer number (610832685).

Almost surely, 2^1221665369 is an apocalyptic number.

It is an amenable number.

1221665369 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221665369 is an equidigital number, since it uses as much as digits as its factorization.

1221665369 is an evil number, because the sum of its binary digits is even.

The product of its digits is 116640, while the sum is 41.

The square root of 1221665369 is about 34952.3299509489. The cubic root of 1221665369 is about 1069.0157102574.

The spelling of 1221665369 in words is "one billion, two hundred twenty-one million, six hundred sixty-five thousand, three hundred sixty-nine".