18385921 has 4 divisors (see below), whose sum is σ = 18492372. Its totient is φ = 18279472.

The previous prime is 18385919. The next prime is 18385931. The reversal of 18385921 is 12958381.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12958381 = 149 ⋅86969.

It can be written as a sum of positive squares in 2 ways, for example, as 17943696 + 442225 = 4236^2 + 665^2 .

It is a cyclic number.

It is not a de Polignac number, because 18385921 - 2¹ = 18385919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18385931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 52966 + ... + 53311.

It is an arithmetic number, because the mean of its divisors is an integer number (4623093).

Almost surely, 2^18385921 is an apocalyptic number.

It is an amenable number.

18385921 is a deficient number, since it is larger than the sum of its proper divisors (106451).

18385921 is a wasteful number, since it uses less digits than its factorization.

18385921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106450.

The product of its digits is 17280, while the sum is 37.

The square root of 18385921 is about 4287.8807119602. The cubic root of 18385921 is about 263.9338725178.

It can be divided in two parts, 18385 and 921, that added together give a triangular number (19306 = T₁₉₆).

The spelling of 18385921 in words is "eighteen million, three hundred eighty-five thousand, nine hundred twenty-one".