55781 has 6 divisors (see below), whose sum is σ = 61446. Its totient is φ = 50600.

The previous prime is 55763. The next prime is 55787. The reversal of 55781 is 18755.

It can be written as a sum of positive squares in only one way, i.e., 43681 + 12100 = 209^2 + 110^2 .

It is not a de Polignac number, because 55781 - 2⁶ = 55717 is a prime.

It is a super-2 number, since 2×55781² = 6223039922, which contains 22 as substring.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 55781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55787) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 110 + ... + 351.

It is an arithmetic number, because the mean of its divisors is an integer number (10241).

2⁵⁵⁷⁸¹ is an apocalyptic number.

It is an amenable number.

55781 is a deficient number, since it is larger than the sum of its proper divisors (5665).

55781 is a wasteful number, since it uses less digits than its factorization.

55781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 483 (or 472 counting only the distinct ones).

The product of its digits is 1400, while the sum is 26.

The square root of 55781 is about 236.1800160894. The cubic root of 55781 is about 38.2086856523.

Subtracting from 55781 its sum of digits (26), we obtain a palindrome (55755).

The spelling of 55781 in words is "fifty-five thousand, seven hundred eighty-one".