1800821 has 8 divisors (see below), whose sum is σ = 2028288. Its totient is φ = 1584000.

The previous prime is 1800811. The next prime is 1800823. The reversal of 1800821 is 1280081.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1800821 - 2¹⁰ = 1799797 is a prime.

It is a Duffinian number.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 1800793 and 1800802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1800823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2300 + ... + 2981.

It is an arithmetic number, because the mean of its divisors is an integer number (253536).

2^1800821 is an apocalyptic number.

1800821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1800821 is a deficient number, since it is larger than the sum of its proper divisors (227467).

1800821 is a wasteful number, since it uses less digits than its factorization.

1800821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5323.

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 1800821 is about 1341.9467202538. The cubic root of 1800821 is about 121.6625314997.

The spelling of 1800821 in words is "one million, eight hundred thousand, eight hundred twenty-one".