1981609 has 12 divisors (see below), whose sum is σ = 2369604. Its totient is φ = 1651104.

The previous prime is 1981607. The next prime is 1981619. The reversal of 1981609 is 9061891.

It can be written as a sum of positive squares in 2 ways, for example, as 1882384 + 99225 = 1372^2 + 315^2 .

It is not a de Polignac number, because 1981609 - 2¹ = 1981607 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981607) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1267 + ... + 2359.

It is an arithmetic number, because the mean of its divisors is an integer number (197467).

2^1981609 is an apocalyptic number.

It is an amenable number.

1981609 is a deficient number, since it is larger than the sum of its proper divisors (387995).

1981609 is a wasteful number, since it uses less digits than its factorization.

1981609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1144 (or 1137 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 34.

The square root of 1981609 is about 1407.6963450972. The cubic root of 1981609 is about 125.6047283776.

The spelling of 1981609 in words is "one million, nine hundred eighty-one thousand, six hundred nine".