1981981 has 4 divisors (see below), whose sum is σ = 2030364. Its totient is φ = 1933600.

The previous prime is 1981963. The next prime is 1981997. The reversal of 1981981 is 1891891.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1891891 = 47 ⋅40253.

It can be written as a sum of positive squares in 2 ways, for example, as 793881 + 1188100 = 891^2 + 1090^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981981 - 2⁵ = 1981949 is a prime.

It is a super-2 number, since 2×1981981² = 7856497368722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1981981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981901) 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 3 ways as a sum of consecutive naturals, for example, 24130 + ... + 24211.

It is an arithmetic number, because the mean of its divisors is an integer number (507591).

2^1981981 is an apocalyptic number.

It is an amenable number.

1981981 is a deficient number, since it is larger than the sum of its proper divisors (48383).

1981981 is an equidigital number, since it uses as much as digits as its factorization.

1981981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48382.

The product of its digits is 5184, while the sum is 37.

The square root of 1981981 is about 1407.8284696653. The cubic root of 1981981 is about 125.6125876535.

It can be divided in two parts, 19819 and 81, that added together give a triangular number (19900 = T₁₉₉).

The spelling of 1981981 in words is "one million, nine hundred eighty-one thousand, nine hundred eighty-one".