18909993 has 16 divisors (see below), whose sum is σ = 25905920. Its totient is φ = 12265344.

The previous prime is 18909991. The next prime is 18910007. The reversal of 18909993 is 39990981.

It is not a de Polignac number, because 18909993 - 2¹ = 18909991 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18909991) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16755 + ... + 17847.

It is an arithmetic number, because the mean of its divisors is an integer number (1619120).

Almost surely, 2^18909993 is an apocalyptic number.

It is an amenable number.

18909993 is a deficient number, since it is larger than the sum of its proper divisors (6995927).

18909993 is a wasteful number, since it uses less digits than its factorization.

18909993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1248.

The product of its (nonzero) digits is 157464, while the sum is 48.

The square root of 18909993 is about 4348.5621761681. The cubic root of 18909993 is about 266.4181384136.

The spelling of 18909993 in words is "eighteen million, nine hundred nine thousand, nine hundred ninety-three".