18308993 has 4 divisors (see below), whose sum is σ = 18326340. Its totient is φ = 18291648.

The previous prime is 18308987. The next prime is 18308999. The reversal of 18308993 is 39980381.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 39980381 = 7 ⋅5711483.

It is an interprime number because it is at equal distance from previous prime (18308987) and next prime (18308999).

It can be written as a sum of positive squares in 2 ways, for example, as 7661824 + 10647169 = 2768^2 + 3263^2 .

It is a cyclic number.

It is not a de Polignac number, because 18308993 - 2⁶ = 18308929 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18308993.

It is not an unprimeable number, because it can be changed into a prime (18308999) 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 3 ways as a sum of consecutive naturals, for example, 6980 + ... + 9237.

It is an arithmetic number, because the mean of its divisors is an integer number (4581585).

Almost surely, 2^18308993 is an apocalyptic number.

It is an amenable number.

18308993 is a deficient number, since it is larger than the sum of its proper divisors (17347).

18308993 is a wasteful number, since it uses less digits than its factorization.

18308993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17346.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 18308993 is about 4278.9009102806. The cubic root of 18308993 is about 263.5652519011.

The spelling of 18308993 in words is "eighteen million, three hundred eight thousand, nine hundred ninety-three".