1221231009 has 4 divisors (see below), whose sum is σ = 1628308016. Its totient is φ = 814154004.

The previous prime is 1221231001. The next prime is 1221231013. The reversal of 1221231009 is 9001321221.

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 an emirpimes, since its reverse is a distinct semiprime: 9001321221 = 3 ⋅3000440407.

It is not a de Polignac number, because 1221231009 - 2³ = 1221231001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221231001) 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 in 3 ways as a sum of consecutive naturals, for example, 203538499 + ... + 203538504.

It is an arithmetic number, because the mean of its divisors is an integer number (407077004).

Almost surely, 2^1221231009 is an apocalyptic number.

It is an amenable number.

1221231009 is a deficient number, since it is larger than the sum of its proper divisors (407077007).

1221231009 is an equidigital number, since it uses as much as digits as its factorization.

1221231009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407077006.

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 1221231009 is about 34946.1157927458. The cubic root of 1221231009 is about 1068.8889999711. Note that the first 3 decimals are identical.

The spelling of 1221231009 in words is "one billion, two hundred twenty-one million, two hundred thirty-one thousand, nine".