205709440 has 64 divisors (see below), whose sum is σ = 493902360. Its totient is φ = 81928192.

The previous prime is 205709429. The next prime is 205709453. The reversal of 205709440 is 44907502.

It can be written as a sum of positive squares in 4 ways, for example, as 187799616 + 17909824 = 13704^2 + 4232^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is a super-2 number, since 2×205709440² = 84632747410227200, which contains 22 as substring.

It is a congruent number.

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, 186972 + ... + 188068.

Almost surely, 2^205709440 is an apocalyptic number.

205709440 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 205709440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (246951180).

205709440 is an abundant number, since it is smaller than the sum of its proper divisors (288192920).

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

205709440 is a wasteful number, since it uses less digits than its factorization.

205709440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1409 (or 1397 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 31.

The square root of 205709440 is about 14342.5743853745. The cubic root of 205709440 is about 590.3162529352.

The spelling of 205709440 in words is "two hundred five million, seven hundred nine thousand, four hundred forty".