1821540 has 48 divisors (see below), whose sum is σ = 5830272. Its totient is φ = 416256.

The previous prime is 1821509. The next prime is 1821541. The reversal of 1821540 is 451281.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (1821541) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1749 + ... + 2588.

It is an arithmetic number, because the mean of its divisors is an integer number (121464).

2^1821540 is an apocalyptic number.

1821540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1821540 is an abundant number, since it is smaller than the sum of its proper divisors (4008732).

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

1821540 is a wasteful number, since it uses less digits than its factorization.

1821540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4356 (or 4354 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 21.

The square root of 1821540 is about 1349.6443976100. The cubic root of 1821540 is about 122.1273417296.

The spelling of 1821540 in words is "one million, eight hundred twenty-one thousand, five hundred forty".