206436821 has 2 divisors, whose sum is σ = 206436822. Its totient is φ = 206436820.

The previous prime is 206436809. The next prime is 206436869. The reversal of 206436821 is 128634602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 104325796 + 102111025 = 10214^2 + 10105^2 .

It is a cyclic number.

It is not a de Polignac number, because 206436821 - 2⁶ = 206436757 is a prime.

It is a super-2 number, since 2×206436821² = 85232322129172082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206430821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103218410 + 103218411.

It is an arithmetic number, because the mean of its divisors is an integer number (103218411).

Almost surely, 2^206436821 is an apocalyptic number.

It is an amenable number.

206436821 is a deficient number, since it is larger than the sum of its proper divisors (1).

206436821 is an equidigital number, since it uses as much as digits as its factorization.

206436821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13824, while the sum is 32.

The square root of 206436821 is about 14367.9094164739. The cubic root of 206436821 is about 591.0112132992.

The spelling of 206436821 in words is "two hundred six million, four hundred thirty-six thousand, eight hundred twenty-one".