18506721 has 8 divisors (see below), whose sum is σ = 25471744. Its totient is φ = 11939760.

The previous prime is 18506717. The next prime is 18506723. The reversal of 18506721 is 12760581.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 18506721 - 2² = 18506717 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 (18506723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 99406 + ... + 99591.

It is an arithmetic number, because the mean of its divisors is an integer number (3183968).

Almost surely, 2^18506721 is an apocalyptic number.

It is an amenable number.

18506721 is a deficient number, since it is larger than the sum of its proper divisors (6965023).

18506721 is a wasteful number, since it uses less digits than its factorization.

18506721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199031.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 18506721 is about 4301.9438629531. The cubic root of 18506721 is about 264.5106478800.

The spelling of 18506721 in words is "eighteen million, five hundred six thousand, seven hundred twenty-one".