1221609 has 4 divisors (see below), whose sum is σ = 1628816. Its totient is φ = 814404.

The previous prime is 1221601. The next prime is 1221631. The reversal of 1221609 is 9061221.

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.

It is not a de Polignac number, because 1221609 - 2³ = 1221601 is a prime.

It is a D-number.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1221601) 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, 203599 + ... + 203604.

It is an arithmetic number, because the mean of its divisors is an integer number (407204).

2^1221609 is an apocalyptic number.

It is an amenable number.

1221609 is a deficient number, since it is larger than the sum of its proper divisors (407207).

1221609 is an equidigital number, since it uses as much as digits as its factorization.

1221609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407206.

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

The square root of 1221609 is about 1105.2642218040. The cubic root of 1221609 is about 106.8999268146.

It can be divided in two parts, 1221 and 609, that added together give a triangular number (1830 = T₆₀).

The spelling of 1221609 in words is "one million, two hundred twenty-one thousand, six hundred nine".