205905921 has 16 divisors (see below), whose sum is σ = 313052544. Its totient is φ = 119257344.

The previous prime is 205905911. The next prime is 205905943. The reversal of 205905921 is 129509502.

205905921 = 450² + 451² + ... + 891².

It is not a de Polignac number, because 205905921 - 2⁹ = 205905409 is a prime.

It is a super-3 number, since 3×205905921³ (a number of 26 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (205905911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 154621 + ... + 155946.

It is an arithmetic number, because the mean of its divisors is an integer number (19565784).

Almost surely, 2^205905921 is an apocalyptic number.

It is an amenable number.

205905921 is a deficient number, since it is larger than the sum of its proper divisors (107146623).

205905921 is a wasteful number, since it uses less digits than its factorization.

205905921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310600.

The product of its (nonzero) digits is 8100, while the sum is 33.

The square root of 205905921 is about 14349.4223228672. The cubic root of 205905921 is about 590.5041377169.

The spelling of 205905921 in words is "two hundred five million, nine hundred five thousand, nine hundred twenty-one".