205999949 has 4 divisors (see below), whose sum is σ = 211024380. Its totient is φ = 200975520.

The previous prime is 205999943. The next prime is 205999973. The reversal of 205999949 is 949999502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 949999502 = 2 ⋅474999751.

It can be written as a sum of positive squares in 2 ways, for example, as 75811849 + 130188100 = 8707^2 + 11410^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205999949 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 205999894 and 205999903.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205999943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2512154 + ... + 2512235.

It is an arithmetic number, because the mean of its divisors is an integer number (52756095).

Almost surely, 2^205999949 is an apocalyptic number.

It is an amenable number.

205999949 is a deficient number, since it is larger than the sum of its proper divisors (5024431).

205999949 is an equidigital number, since it uses as much as digits as its factorization.

205999949 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5024430.

The product of its (nonzero) digits is 2361960, while the sum is 56.

The square root of 205999949 is about 14352.6983177380. The cubic root of 205999949 is about 590.5940096241.

The spelling of 205999949 in words is "two hundred five million, nine hundred ninety-nine thousand, nine hundred forty-nine".