1608721 has 4 divisors (see below), whose sum is σ = 1611700. Its totient is φ = 1605744.

The previous prime is 1608713. The next prime is 1608743. The reversal of 1608721 is 1278061.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1278061 = 257 ⋅4973.

It can be written as a sum of positive squares in 2 ways, for example, as 132496 + 1476225 = 364^2 + 1215^2 .

It is a cyclic number.

It is not a de Polignac number, because 1608721 - 2³ = 1608713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1608751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 426 + ... + 1843.

It is an arithmetic number, because the mean of its divisors is an integer number (402925).

2^1608721 is an apocalyptic number.

It is an amenable number.

1608721 is a deficient number, since it is larger than the sum of its proper divisors (2979).

1608721 is an equidigital number, since it uses as much as digits as its factorization.

1608721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2978.

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 1608721 is about 1268.3536573054. The cubic root of 1608721 is about 117.1728275912.

The spelling of 1608721 in words is "one million, six hundred eight thousand, seven hundred twenty-one".