205609866 has 128 divisors (see below), whose sum is σ = 555393024. Its totient is φ = 49105920.

The previous prime is 205609813. The next prime is 205609879. The reversal of 205609866 is 668906502.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 368860 + ... + 369416.

It is an arithmetic number, because the mean of its divisors is an integer number (4339008).

Almost surely, 2^205609866 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 205609866, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (277696512).

205609866 is an abundant number, since it is smaller than the sum of its proper divisors (349783158).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

205609866 is a wasteful number, since it uses less digits than its factorization.

205609866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 644.

The product of its (nonzero) digits is 155520, while the sum is 42.

The square root of 205609866 is about 14339.1026915913. The cubic root of 205609866 is about 590.2209897048.

The spelling of 205609866 in words is "two hundred five million, six hundred nine thousand, eight hundred sixty-six".