1681820 has 48 divisors (see below), whose sum is σ = 4148928. Its totient is φ = 560640.

The previous prime is 1681817. The next prime is 1681837. The reversal of 1681820 is 281861.

1681820 = 455² + 456² + ... + 462².

It is a self number, because there is not a number n which added to its sum of digits gives 1681820.

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 15 ways as a sum of consecutive naturals, for example, 5594 + ... + 5886.

It is an arithmetic number, because the mean of its divisors is an integer number (86436).

2^1681820 is an apocalyptic number.

1681820 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 1681820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2074464).

1681820 is an abundant number, since it is smaller than the sum of its proper divisors (2467108).

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

1681820 is a wasteful number, since it uses less digits than its factorization.

1681820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350 (or 348 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 1681820 is about 1296.8500298801. The cubic root of 1681820 is about 118.9213518879.

The spelling of 1681820 in words is "one million, six hundred eighty-one thousand, eight hundred twenty".