205666421 has 2 divisors, whose sum is σ = 205666422. Its totient is φ = 205666420.

The previous prime is 205666411. The next prime is 205666453. The reversal of 205666421 is 124666502.

It is an a-pointer prime, because the next prime (205666453) can be obtained adding 205666421 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 149206225 + 56460196 = 12215^2 + 7514^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205666421 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (205666411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 102833210 + 102833211.

It is an arithmetic number, because the mean of its divisors is an integer number (102833211).

Almost surely, 2^205666421 is an apocalyptic number.

It is an amenable number.

205666421 is a deficient number, since it is larger than the sum of its proper divisors (1).

205666421 is an equidigital number, since it uses as much as digits as its factorization.

205666421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 32.

The square root of 205666421 is about 14341.0746110604. The cubic root of 205666421 is about 590.2751000914.

The spelling of 205666421 in words is "two hundred five million, six hundred sixty-six thousand, four hundred twenty-one".