2181820 has 36 divisors (see below), whose sum is σ = 4770360. Its totient is φ = 837984.

The previous prime is 2181737. The next prime is 2181833. The reversal of 2181820 is 281812.

2181820 is nontrivially palindromic in base 3 and base 9.

It is a zygodrome in base 3.

It is a junction number, because it is equal to n+sod(n) for n = 2181791 and 2181800.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36951 + ... + 37009.

It is an arithmetic number, because the mean of its divisors is an integer number (132510).

2^2181820 is an apocalyptic number.

2181820 is a gapful number since it is divisible by the number (20) 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 2181820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2385180).

2181820 is an abundant number, since it is smaller than the sum of its proper divisors (2588540).

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

2181820 is a wasteful number, since it uses less digits than its factorization.

2181820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 22.

The square root of 2181820 is about 1477.0985072093. The cubic root of 2181820 is about 129.6998994773.

The spelling of 2181820 in words is "two million, one hundred eighty-one thousand, eight hundred twenty".