1221365909 has 2 divisors, whose sum is σ = 1221365910. Its totient is φ = 1221365908.

The previous prime is 1221365801. The next prime is 1221365917. The reversal of 1221365909 is 9095631221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 669256900 + 552109009 = 25870^2 + 23497^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221365909 - 2²⁸ = 952930453 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221365939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610682954 + 610682955.

It is an arithmetic number, because the mean of its divisors is an integer number (610682955).

Almost surely, 2^1221365909 is an apocalyptic number.

It is an amenable number.

1221365909 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221365909 is an equidigital number, since it uses as much as digits as its factorization.

1221365909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 29160, while the sum is 38.

The square root of 1221365909 is about 34948.0458538099. The cubic root of 1221365909 is about 1068.9283558385.

The spelling of 1221365909 in words is "one billion, two hundred twenty-one million, three hundred sixty-five thousand, nine hundred nine".