1801820 has 24 divisors (see below), whose sum is σ = 3949344. Its totient is φ = 689216.

The previous prime is 1801819. The next prime is 1801823. The reversal of 1801820 is 281081.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 1801792 and 1801801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1801823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1499 + ... + 2418.

It is an arithmetic number, because the mean of its divisors is an integer number (164556).

2^1801820 is an apocalyptic number.

1801820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1801820 is an abundant number, since it is smaller than the sum of its proper divisors (2147524).

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

1801820 is a wasteful number, since it uses less digits than its factorization.

1801820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3949 (or 3947 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 1801820 is about 1342.3188890871. The cubic root of 1801820 is about 121.6850246480.

The spelling of 1801820 in words is "one million, eight hundred one thousand, eight hundred twenty".