55555551 has 20 divisors (see below), whose sum is σ = 84761952. Its totient is φ = 36246528.

The previous prime is 55555547. The next prime is 55555553. The reversal of 55555551 is 15555555.

It is a happy number.

55555551 is a `hidden beast` number, since 5 + 55 + 55 + 551 = 666.

It is not a de Polignac number, because 55555551 - 2² = 55555547 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (55555553) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3490 + ... + 11103.

Almost surely, 2^55555551 is an apocalyptic number.

55555551 is a deficient number, since it is larger than the sum of its proper divisors (29206401).

55555551 is a wasteful number, since it uses less digits than its factorization.

55555551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14652 (or 14643 counting only the distinct ones).

The product of its digits is 78125, while the sum is 36.

The square root of 55555551 is about 7453.5596194033. The cubic root of 55555551 is about 381.5714037548.

The spelling of 55555551 in words is "fifty-five million, five hundred fifty-five thousand, five hundred fifty-one".