205663891 has 2 divisors, whose sum is σ = 205663892. Its totient is φ = 205663890.

The previous prime is 205663867. The next prime is 205663897. The reversal of 205663891 is 198366502.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 205663891 - 2⁹ = 205663379 is a prime.

It is a super-2 number, since 2×205663891² = 84595272122519762, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (205663897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102831945 + 102831946.

It is an arithmetic number, because the mean of its divisors is an integer number (102831946).

Almost surely, 2^205663891 is an apocalyptic number.

205663891 is a deficient number, since it is larger than the sum of its proper divisors (1).

205663891 is an equidigital number, since it uses as much as digits as its factorization.

205663891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 77760, while the sum is 40.

The square root of 205663891 is about 14340.9864026154. The cubic root of 205663891 is about 590.2726796637.

The spelling of 205663891 in words is "two hundred five million, six hundred sixty-three thousand, eight hundred ninety-one".