206649991 has 2 divisors, whose sum is σ = 206649992. Its totient is φ = 206649990.

The previous prime is 206649983. The next prime is 206650001. The reversal of 206649991 is 199946602.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 206649991 - 2³ = 206649983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (206649941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103324995 + 103324996.

It is an arithmetic number, because the mean of its divisors is an integer number (103324996).

Almost surely, 2^206649991 is an apocalyptic number.

206649991 is a deficient number, since it is larger than the sum of its proper divisors (1).

206649991 is an equidigital number, since it uses as much as digits as its factorization.

206649991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 209952, while the sum is 46.

The square root of 206649991 is about 14375.3257702217. The cubic root of 206649991 is about 591.2145725636.

The spelling of 206649991 in words is "two hundred six million, six hundred forty-nine thousand, nine hundred ninety-one".