18403821 has 8 divisors (see below), whose sum is σ = 27264960. Its totient is φ = 12269196.

The previous prime is 18403813. The next prime is 18403823. The reversal of 18403821 is 12830481.

It is not a de Polignac number, because 18403821 - 2³ = 18403813 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 681623 = 18403821 / (1 + 8 + 4 + 0 + 3 + 8 + 2 + 1).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18403823) 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, 340785 + ... + 340838.

It is an arithmetic number, because the mean of its divisors is an integer number (3408120).

Almost surely, 2^18403821 is an apocalyptic number.

It is an amenable number.

18403821 is a deficient number, since it is larger than the sum of its proper divisors (8861139).

18403821 is an equidigital number, since it uses as much as digits as its factorization.

18403821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 681632 (or 681626 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 18403821 is about 4289.9674823942. The cubic root of 18403821 is about 264.0194975269.

The spelling of 18403821 in words is "eighteen million, four hundred three thousand, eight hundred twenty-one".