1821644 has 24 divisors (see below), whose sum is σ = 3662400. Its totient is φ = 784080.

The previous prime is 1821641. The next prime is 1821649. The reversal of 1821644 is 4461281.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1821641) 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 7 ways as a sum of consecutive naturals, for example, 254 + ... + 1925.

It is an arithmetic number, because the mean of its divisors is an integer number (152600).

2^1821644 is an apocalyptic number.

It is an amenable number.

1821644 is an abundant number, since it is smaller than the sum of its proper divisors (1840756).

1821644 is a wasteful number, since it uses less digits than its factorization.

1821644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2213 (or 2211 counting only the distinct ones).

The product of its digits is 1536, while the sum is 26.

The square root of 1821644 is about 1349.6829257274. The cubic root of 1821644 is about 122.1296659538.

The spelling of 1821644 in words is "one million, eight hundred twenty-one thousand, six hundred forty-four".