1209865009 has 4 divisors (see below), whose sum is σ = 1209950704. Its totient is φ = 1209779316.

The previous prime is 1209865003. The next prime is 1209865031. The reversal of 1209865009 is 9005689021.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1209865009 - 2²¹ = 1207767857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1209865003) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16107 + ... + 51760.

It is an arithmetic number, because the mean of its divisors is an integer number (302487676).

Almost surely, 2^1209865009 is an apocalyptic number.

It is an amenable number.

1209865009 is a deficient number, since it is larger than the sum of its proper divisors (85695).

1209865009 is an equidigital number, since it uses as much as digits as its factorization.

1209865009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85694.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 1209865009 is about 34783.1138485329. The cubic root of 1209865009 is about 1065.5626080996.

The spelling of 1209865009 in words is "one billion, two hundred nine million, eight hundred sixty-five thousand, nine".