1820645 has 4 divisors (see below), whose sum is σ = 2184780. Its totient is φ = 1456512.

The previous prime is 1820641. The next prime is 1820647. The reversal of 1820645 is 5460281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5460281 = 17 ⋅321193.

It can be written as a sum of positive squares in 2 ways, for example, as 1044484 + 776161 = 1022^2 + 881^2 .

It is a cyclic number.

It is not a de Polignac number, because 1820645 - 2² = 1820641 is a prime.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1820641) 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, 182060 + ... + 182069.

It is an arithmetic number, because the mean of its divisors is an integer number (546195).

2^1820645 is an apocalyptic number.

It is an amenable number.

1820645 is a deficient number, since it is larger than the sum of its proper divisors (364135).

1820645 is an equidigital number, since it uses as much as digits as its factorization.

1820645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364134.

The product of its (nonzero) digits is 1920, while the sum is 26.

The square root of 1820645 is about 1349.3127880518. The cubic root of 1820645 is about 122.1073363353.

The spelling of 1820645 in words is "one million, eight hundred twenty thousand, six hundred forty-five".