205781890 has 16 divisors (see below), whose sum is σ = 375482808. Its totient is φ = 81184896.

The previous prime is 205781887. The next prime is 205781921. The reversal of 205781890 is 98187502.

205781890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 195916009 + 9865881 = 13997^2 + 3141^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 140217 + ... + 141676.

Almost surely, 2^205781890 is an apocalyptic number.

205781890 is a deficient number, since it is larger than the sum of its proper divisors (169700918).

205781890 is a wasteful number, since it uses less digits than its factorization.

205781890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 281973.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 205781890 is about 14345.0998602310. The cubic root of 205781890 is about 590.3855471017.

The spelling of 205781890 in words is "two hundred five million, seven hundred eighty-one thousand, eight hundred ninety".