1816981 has 4 divisors (see below), whose sum is σ = 1819692. Its totient is φ = 1814272.

The previous prime is 1816979. The next prime is 1816987. The reversal of 1816981 is 1896181.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 1136356 + 680625 = 1066^2 + 825^2 .

It is a cyclic number.

It is not a de Polignac number, because 1816981 - 2¹ = 1816979 is a prime.

It is a super-2 number, since 2×1816981² = 6602839908722, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1816987) 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, 471 + ... + 1963.

It is an arithmetic number, because the mean of its divisors is an integer number (454923).

2^1816981 is an apocalyptic number.

It is an amenable number.

1816981 is a deficient number, since it is larger than the sum of its proper divisors (2711).

1816981 is a wasteful number, since it uses less digits than its factorization.

1816981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2710.

The product of its digits is 3456, while the sum is 34.

The square root of 1816981 is about 1347.9543760825. The cubic root of 1816981 is about 122.0253687279.

The spelling of 1816981 in words is "one million, eight hundred sixteen thousand, nine hundred eighty-one".