1981540 has 24 divisors (see below), whose sum is σ = 4540032. Its totient is φ = 720480.

The previous prime is 1981523. The next prime is 1981543. The reversal of 1981540 is 451891.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 1981499 and 1981508.

It is not an unprimeable number, because it can be changed into a prime (1981543) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4284 + ... + 4723.

It is an arithmetic number, because the mean of its divisors is an integer number (189168).

2^1981540 is an apocalyptic number.

1981540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1981540 is an abundant number, since it is smaller than the sum of its proper divisors (2558492).

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

1981540 is a wasteful number, since it uses less digits than its factorization.

1981540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9027 (or 9025 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 28.

The square root of 1981540 is about 1407.6718367574. The cubic root of 1981540 is about 125.6032705005.

The spelling of 1981540 in words is "one million, nine hundred eighty-one thousand, five hundred forty".