255405991 has 2 divisors, whose sum is σ = 255405992. Its totient is φ = 255405990.

The previous prime is 255405989. The next prime is 255406003. The reversal of 255405991 is 199504552.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 255405991 - 2¹ = 255405989 is a prime.

Together with 255405989, it forms a pair of twin primes.

It is equal to p_13958761 and since 255405991 and 13958761 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (255405901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 127702995 + 127702996.

It is an arithmetic number, because the mean of its divisors is an integer number (127702996).

Almost surely, 2^255405991 is an apocalyptic number.

255405991 is a deficient number, since it is larger than the sum of its proper divisors (1).

255405991 is an equidigital number, since it uses as much as digits as its factorization.

255405991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 81000, while the sum is 40.

The square root of 255405991 is about 15981.4264382126. The cubic root of 255405991 is about 634.4689308071.

The spelling of 255405991 in words is "two hundred fifty-five million, four hundred five thousand, nine hundred ninety-one".