1981409 has 2 divisors, whose sum is σ = 1981410. Its totient is φ = 1981408.

The previous prime is 1981403. The next prime is 1981417. The reversal of 1981409 is 9041891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1221025 + 760384 = 1105^2 + 872^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981409 - 2⁴ = 1981393 is a prime.

It is a super-3 number, since 3×1981409³ = 23336925978499202787, which contains 333 as substring.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1981403) 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 as a sum of consecutive naturals, namely, 990704 + 990705.

It is an arithmetic number, because the mean of its divisors is an integer number (990705).

2^1981409 is an apocalyptic number.

It is an amenable number.

1981409 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981409 is an equidigital number, since it uses as much as digits as its factorization.

1981409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 32.

The square root of 1981409 is about 1407.6253052570. The cubic root of 1981409 is about 125.6005025539.

The spelling of 1981409 in words is "one million, nine hundred eighty-one thousand, four hundred nine".