55787781 has 32 divisors (see below), whose sum is σ = 90547200. Its totient is φ = 29842560.

The previous prime is 55787777. The next prime is 55787803. The reversal of 55787781 is 18778755.

It is a happy number.

It is not a de Polignac number, because 55787781 - 2² = 55787777 is a prime.

It is a super-2 number, since 2×55787781² = 6224553017807922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 55787781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55787741) 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, 34726 + ... + 36296.

It is an arithmetic number, because the mean of its divisors is an integer number (2829600).

Almost surely, 2^55787781 is an apocalyptic number.

It is an amenable number.

55787781 is a deficient number, since it is larger than the sum of its proper divisors (34759419).

55787781 is a wasteful number, since it uses less digits than its factorization.

55787781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1689.

The product of its digits is 548800, while the sum is 48.

The square root of 55787781 is about 7469.1218359323. The cubic root of 55787781 is about 382.1023386526.

The spelling of 55787781 in words is "fifty-five million, seven hundred eighty-seven thousand, seven hundred eighty-one".