205991640 has 128 divisors (see below), whose sum is σ = 710424000. Its totient is φ = 53028864.

The previous prime is 205991627. The next prime is 205991651. The reversal of 205991640 is 46199502.

205991640 is a `hidden beast` number, since 2 + 0 + 5 + 9 + 9 + 1 + 640 = 666.

205991640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 205991595 and 205991604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28032 + ... + 34608.

Almost surely, 2^205991640 is an apocalyptic number.

205991640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 205991640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (355212000).

205991640 is an abundant number, since it is smaller than the sum of its proper divisors (504432360).

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

205991640 is a wasteful number, since it uses less digits than its factorization.

205991640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6626 (or 6616 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 205991640 is about 14352.4088570525. The cubic root of 205991640 is about 590.5860689885.

The spelling of 205991640 in words is "two hundred five million, nine hundred ninety-one thousand, six hundred forty".