18342721 has 4 divisors (see below), whose sum is σ = 18444244. Its totient is φ = 18241200.

The previous prime is 18342691. The next prime is 18342743. The reversal of 18342721 is 12724381.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7485696 + 10857025 = 2736^2 + 3295^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18342721 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 18342721.

It is not an unprimeable number, because it can be changed into a prime (18322721) 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, 50490 + ... + 50851.

It is an arithmetic number, because the mean of its divisors is an integer number (4611061).

Almost surely, 2^18342721 is an apocalyptic number.

It is an amenable number.

18342721 is a deficient number, since it is larger than the sum of its proper divisors (101523).

18342721 is a wasteful number, since it uses less digits than its factorization.

18342721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101522.

The product of its digits is 2688, while the sum is 28.

The square root of 18342721 is about 4282.8402958784. The cubic root of 18342721 is about 263.7269952907.

The spelling of 18342721 in words is "eighteen million, three hundred forty-two thousand, seven hundred twenty-one".