1211809 has 4 divisors (see below), whose sum is σ = 1214020. Its totient is φ = 1209600.

The previous prime is 1211807. The next prime is 1211813. The reversal of 1211809 is 9081121.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 115600 + 1096209 = 340^2 + 1047^2 .

It is a cyclic number.

It is not a de Polignac number, because 1211809 - 2¹ = 1211807 is a prime.

It is a Duffinian number.

It is a plaindrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 1211809.

It is not an unprimeable number, because it can be changed into a prime (1211807) 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, 409 + ... + 1609.

It is an arithmetic number, because the mean of its divisors is an integer number (303505).

2^1211809 is an apocalyptic number.

It is an amenable number.

1211809 is a deficient number, since it is larger than the sum of its proper divisors (2211).

1211809 is a wasteful number, since it uses less digits than its factorization.

1211809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2210.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 1211809 is about 1100.8219656239. The cubic root of 1211809 is about 106.6133012136.

The spelling of 1211809 in words is "one million, two hundred eleven thousand, eight hundred nine".