205645891 has 16 divisors (see below), whose sum is σ = 230681088. Its totient is φ = 181742400.

The previous prime is 205645879. The next prime is 205645897. The reversal of 205645891 is 198546502.

It is a cyclic number.

It is not a de Polignac number, because 205645891 - 2¹⁹ = 205121603 is a prime.

It is not an unprimeable number, because it can be changed into a prime (205645897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55210 + ... + 58816.

It is an arithmetic number, because the mean of its divisors is an integer number (14417568).

Almost surely, 2^205645891 is an apocalyptic number.

205645891 is a deficient number, since it is larger than the sum of its proper divisors (25035197).

205645891 is a wasteful number, since it uses less digits than its factorization.

205645891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3762.

The product of its (nonzero) digits is 86400, while the sum is 40.

The square root of 205645891 is about 14340.3588169892. The cubic root of 205645891 is about 590.2554586562.

The spelling of 205645891 in words is "two hundred five million, six hundred forty-five thousand, eight hundred ninety-one".