205781640 has 64 divisors (see below), whose sum is σ = 623376000. Its totient is φ = 54339072.

The previous prime is 205781623. The next prime is 205781657. The reversal of 205781640 is 46187502.

It is an interprime number because it is at equal distance from previous prime (205781623) and next prime (205781657).

It is a super-2 number, since 2×205781640² = 84692166722179200, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4036 + ... + 20684.

It is an arithmetic number, because the mean of its divisors is an integer number (9740250).

Almost surely, 2^205781640 is an apocalyptic number.

205781640 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 205781640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (311688000).

205781640 is an abundant number, since it is smaller than the sum of its proper divisors (417594360).

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

205781640 is a wasteful number, since it uses less digits than its factorization.

205781640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16766 (or 16762 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 33.

The square root of 205781640 is about 14345.0911464515. The cubic root of 205781640 is about 590.3853080193.

The spelling of 205781640 in words is "two hundred five million, seven hundred eighty-one thousand, six hundred forty".