55518781 has 4 divisors (see below), whose sum is σ = 55676412. Its totient is φ = 55361152.

The previous prime is 55518761. The next prime is 55518829. The reversal of 55518781 is 18781555.

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 34035556 + 21483225 = 5834^2 + 4635^2 .

It is a cyclic number.

It is not a de Polignac number, because 55518781 - 2⁹ = 55518269 is a prime.

It is a super-2 number, since 2×55518781² = 6164670087451922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55518721) 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, 78286 + ... + 78991.

It is an arithmetic number, because the mean of its divisors is an integer number (13919103).

Almost surely, 2^55518781 is an apocalyptic number.

It is an amenable number.

55518781 is a deficient number, since it is larger than the sum of its proper divisors (157631).

55518781 is a wasteful number, since it uses less digits than its factorization.

55518781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157630.

The product of its digits is 56000, while the sum is 40.

The square root of 55518781 is about 7451.0926044440. The cubic root of 55518781 is about 381.4872028857.

The spelling of 55518781 in words is "fifty-five million, five hundred eighteen thousand, seven hundred eighty-one".