1821664 has 48 divisors (see below), whose sum is σ = 4021920. Its totient is φ = 806400.

The previous prime is 1821649. The next prime is 1821679. The reversal of 1821664 is 4661281.

It is an interprime number because it is at equal distance from previous prime (1821649) and next prime (1821679).

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11989 + ... + 12139.

It is an arithmetic number, because the mean of its divisors is an integer number (83790).

2^1821664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1821664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2010960).

1821664 is an abundant number, since it is smaller than the sum of its proper divisors (2200256).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1821664 is a wasteful number, since it uses less digits than its factorization.

1821664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203 (or 195 counting only the distinct ones).

The product of its digits is 2304, while the sum is 28.

The square root of 1821664 is about 1349.6903348546. The cubic root of 1821664 is about 122.1301129098.

It can be divided in two parts, 1821 and 664, that added together give a triangular number (2485 = T₇₀).

The spelling of 1821664 in words is "one million, eight hundred twenty-one thousand, six hundred sixty-four".