7218321 has 8 divisors (see below), whose sum is σ = 10499424. Its totient is φ = 4374720.

The previous prime is 7218317. The next prime is 7218331. The reversal of 7218321 is 1238127.

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

It is not a de Polignac number, because 7218321 - 2² = 7218317 is a prime.

It is an alternating number because its digits alternate between odd and even.

7218321 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 7218291 and 7218300.

It is not an unprimeable number, because it can be changed into a prime (7218311) 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, 109336 + ... + 109401.

It is an arithmetic number, because the mean of its divisors is an integer number (1312428).

Almost surely, 2^7218321 is an apocalyptic number.

It is an amenable number.

7218321 is a deficient number, since it is larger than the sum of its proper divisors (3281103).

7218321 is a wasteful number, since it uses less digits than its factorization.

7218321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218751.

The product of its digits is 672, while the sum is 24.

The square root of 7218321 is about 2686.6933207942. The cubic root of 7218321 is about 193.2615227425.

The spelling of 7218321 in words is "seven million, two hundred eighteen thousand, three hundred twenty-one".