1211805 has 24 divisors (see below), whose sum is σ = 2401152. Its totient is φ = 553824.

The previous prime is 1211797. The next prime is 1211807. The reversal of 1211805 is 5081121.

It is not a de Polignac number, because 1211805 - 2³ = 1211797 is a prime.

It is an Ulam number.

It is a congruent number.

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 (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1609 + ... + 2238.

It is an arithmetic number, because the mean of its divisors is an integer number (100048).

2^1211805 is an apocalyptic number.

1211805 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1211805 is a deficient number, since it is larger than the sum of its proper divisors (1189347).

1211805 is a wasteful number, since it uses less digits than its factorization.

1211805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3865 (or 3862 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 1211805 is about 1100.8201487982. The cubic root of 1211805 is about 106.6131839087.

Adding to 1211805 its reverse (5081121), we get a palindrome (6292926).

It can be divided in two parts, 1211 and 805, that added together give a triangular number (2016 = T₆₃).

The spelling of 1211805 in words is "one million, two hundred eleven thousand, eight hundred five".