1609921 has 4 divisors (see below), whose sum is σ = 1628100. Its totient is φ = 1591744.

The previous prime is 1609913. The next prime is 1609969. The reversal of 1609921 is 1299061.

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 929296 + 680625 = 964^2 + 825^2 .

It is a cyclic number.

It is not a de Polignac number, because 1609921 - 2³ = 1609913 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1609921.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1609901) 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, 8956 + ... + 9133.

It is an arithmetic number, because the mean of its divisors is an integer number (407025).

2^1609921 is an apocalyptic number.

It is an amenable number.

1609921 is a deficient number, since it is larger than the sum of its proper divisors (18179).

1609921 is an equidigital number, since it uses as much as digits as its factorization.

1609921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18178.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1609921 is about 1268.8266233020. The cubic root of 1609921 is about 117.2019547562.

The spelling of 1609921 in words is "one million, six hundred nine thousand, nine hundred twenty-one".