1209840 has 60 divisors (see below), whose sum is σ = 3804072. Its totient is φ = 318080.

The previous prime is 1209821. The next prime is 1209841. The reversal of 1209840 is 489021.

It is a tau number, because it is divible by the number of its divisors (60).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 1209840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1209841) 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 11 ways as a sum of consecutive naturals, for example, 17005 + ... + 17075.

2^1209840 is an apocalyptic number.

1209840 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1209840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1902036).

1209840 is an abundant number, since it is smaller than the sum of its proper divisors (2594232).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1209840 is an equidigital number, since it uses as much as digits as its factorization.

1209840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158 (or 81 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 24.

The square root of 1209840 is about 1099.9272703229. The cubic root of 1209840 is about 106.5555266003. Note that the first 4 decimals are identical.

The spelling of 1209840 in words is "one million, two hundred nine thousand, eight hundred forty".