1821240 has 48 divisors (see below), whose sum is σ = 5920200. Its totient is φ = 485568.

The previous prime is 1821233. The next prime is 1821257. The reversal of 1821240 is 421281.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

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, 2170 + ... + 2889.

2^1821240 is an apocalyptic number.

1821240 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821240 is an abundant number, since it is smaller than the sum of its proper divisors (4098960).

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

1821240 is a wasteful number, since it uses less digits than its factorization.

1821240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5076 (or 5069 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 1821240 is about 1349.5332526470. The cubic root of 1821240 is about 122.1206367411.

The spelling of 1821240 in words is "one million, eight hundred twenty-one thousand, two hundred forty".