1981006409 has 4 divisors (see below), whose sum is σ = 1985418900. Its totient is φ = 1976593920.

The previous prime is 1981006403. The next prime is 1981006421. The reversal of 1981006409 is 9046001891.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 892336384 + 1088670025 = 29872^2 + 32995^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981006409 - 2⁴ = 1981006393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981006403) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2205572 + ... + 2206469.

It is an arithmetic number, because the mean of its divisors is an integer number (496354725).

Almost surely, 2^1981006409 is an apocalyptic number.

It is an amenable number.

1981006409 is a deficient number, since it is larger than the sum of its proper divisors (4412491).

1981006409 is an equidigital number, since it uses as much as digits as its factorization.

1981006409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4412490.

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 1981006409 is about 44508.4981660806. The cubic root of 1981006409 is about 1255.9199529851.

The spelling of 1981006409 in words is "one billion, nine hundred eighty-one million, six thousand, four hundred nine".