1981820 has 24 divisors (see below), whose sum is σ = 4191264. Its totient is φ = 787136.

The previous prime is 1981813. The next prime is 1981853. The reversal of 1981820 is 281891.

It is a super-2 number, since 2×1981820² = 7855221024800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3689 + ... + 4191.

It is an arithmetic number, because the mean of its divisors is an integer number (174636).

2^1981820 is an apocalyptic number.

1981820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1981820 is an abundant number, since it is smaller than the sum of its proper divisors (2209444).

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

1981820 is a wasteful number, since it uses less digits than its factorization.

1981820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 709 (or 707 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 1981820 is about 1407.7712882425. The cubic root of 1981820 is about 125.6091863134.

The spelling of 1981820 in words is "one million, nine hundred eighty-one thousand, eight hundred twenty".