1981021 has 6 divisors (see below), whose sum is σ = 2304510. Its totient is φ = 1697976.

The previous prime is 1980991. The next prime is 1981037. The reversal of 1981021 is 1201891.

It can be written as a sum of positive squares in only one way, i.e., 1920996 + 60025 = 1386^2 + 245^2 .

It is not a de Polignac number, because 1981021 - 2¹³ = 1972829 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1980983 and 1981001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 20166 + ... + 20263.

It is an arithmetic number, because the mean of its divisors is an integer number (384085).

2^1981021 is an apocalyptic number.

It is an amenable number.

1981021 is a deficient number, since it is larger than the sum of its proper divisors (323489).

1981021 is an equidigital number, since it uses as much as digits as its factorization.

1981021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40443 (or 40436 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 1981021 is about 1407.4874777418. The cubic root of 1981021 is about 125.5923036449.

The spelling of 1981021 in words is "one million, nine hundred eighty-one thousand, twenty-one".