55218640 has 20 divisors (see below), whose sum is σ = 128383524. Its totient is φ = 22087424.

The previous prime is 55218629. The next prime is 55218649. The reversal of 55218640 is 4681255.

It can be written as a sum of positive squares in 2 ways, for example, as 24482704 + 30735936 = 4948^2 + 5544^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55218649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 345037 + ... + 345196.

Almost surely, 2^55218640 is an apocalyptic number.

It is an amenable number.

55218640 is an abundant number, since it is smaller than the sum of its proper divisors (73164884).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

55218640 is a wasteful number, since it uses less digits than its factorization.

55218640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 690246 (or 690240 counting only the distinct ones).

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 55218640 is about 7430.9245723530. The cubic root of 55218640 is about 380.7985055728.

Adding to 55218640 its reverse (4681255), we get a palindrome (59899895).

It can be divided in two parts, 5521 and 8640, that added together give a square (14161 = 119²).

The spelling of 55218640 in words is "fifty-five million, two hundred eighteen thousand, six hundred forty".