55218321 has 32 divisors (see below), whose sum is σ = 84480000. Its totient is φ = 35625744.

The previous prime is 55218307. The next prime is 55218337. The reversal of 55218321 is 12381255.

It is a happy number.

It is not a de Polignac number, because 55218321 - 2⁶ = 55218257 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (55218301) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 230920 + ... + 231158.

It is an arithmetic number, because the mean of its divisors is an integer number (2640000).

Almost surely, 2^55218321 is an apocalyptic number.

It is an amenable number.

55218321 is a deficient number, since it is larger than the sum of its proper divisors (29261679).

55218321 is a wasteful number, since it uses less digits than its factorization.

55218321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 490 (or 484 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 55218321 is about 7430.9031079674. The cubic root of 55218321 is about 380.7977722760.

Adding to 55218321 its reverse (12381255), we get a palindrome (67599576).

The spelling of 55218321 in words is "fifty-five million, two hundred eighteen thousand, three hundred twenty-one".