205555551 has 32 divisors (see below), whose sum is σ = 296616960. Its totient is φ = 126157824.

The previous prime is 205555549. The next prime is 205555561. The reversal of 205555551 is 155555502.

It is not a de Polignac number, because 205555551 - 2¹ = 205555549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205555501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 656571 + ... + 656883.

It is an arithmetic number, because the mean of its divisors is an integer number (9269280).

Almost surely, 2^205555551 is an apocalyptic number.

205555551 is a deficient number, since it is larger than the sum of its proper divisors (91061409).

205555551 is a wasteful number, since it uses less digits than its factorization.

205555551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 575.

The product of its (nonzero) digits is 31250, while the sum is 33.

The square root of 205555551 is about 14337.2086195326. The cubic root of 205555551 is about 590.1690131517.

It can be divided in two parts, 20555 and 5551, that added together give a triangular number (26106 = T₂₂₈).

The spelling of 205555551 in words is "two hundred five million, five hundred fifty-five thousand, five hundred fifty-one".