18916321 has 4 divisors (see below), whose sum is σ = 18954432. Its totient is φ = 18878212.

The previous prime is 18916309. The next prime is 18916351. The reversal of 18916321 is 12361981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12361981 = 977 ⋅12653.

It is a cyclic number.

It is not a de Polignac number, because 18916321 - 2²¹ = 16819169 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18916301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18301 + ... + 19306.

It is an arithmetic number, because the mean of its divisors is an integer number (4738608).

Almost surely, 2^18916321 is an apocalyptic number.

It is an amenable number.

18916321 is a deficient number, since it is larger than the sum of its proper divisors (38111).

18916321 is an equidigital number, since it uses as much as digits as its factorization.

18916321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38110.

The product of its digits is 2592, while the sum is 31.

The square root of 18916321 is about 4349.2897121254. The cubic root of 18916321 is about 266.4478529665.

The spelling of 18916321 in words is "eighteen million, nine hundred sixteen thousand, three hundred twenty-one".