1861609 has 4 divisors (see below), whose sum is σ = 1864404. Its totient is φ = 1858816.

The previous prime is 1861591. The next prime is 1861621. The reversal of 1861609 is 9061681.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 9061681 = 653 ⋅13877.

It can be written as a sum of positive squares in 2 ways, for example, as 1265625 + 595984 = 1125^2 + 772^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1861609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1861649) 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 in 3 ways as a sum of consecutive naturals, for example, 249 + ... + 1945.

It is an arithmetic number, because the mean of its divisors is an integer number (466101).

2^1861609 is an apocalyptic number.

It is an amenable number.

1861609 is a deficient number, since it is larger than the sum of its proper divisors (2795).

1861609 is a wasteful number, since it uses less digits than its factorization.

1861609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2794.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 1861609 is about 1364.4079302027. The cubic root of 1861609 is about 123.0163461211.

The spelling of 1861609 in words is "one million, eight hundred sixty-one thousand, six hundred nine".