205640640 has 112 divisors (see below), whose sum is σ = 725484960. Its totient is φ = 54835200.

The previous prime is 205640623. The next prime is 205640671. The reversal of 205640640 is 46046502.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3261 + ... + 20540.

Almost surely, 2^205640640 is an apocalyptic number.

205640640 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 205640640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (362742480).

205640640 is an abundant number, since it is smaller than the sum of its proper divisors (519844320).

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

205640640 is a wasteful number, since it uses less digits than its factorization.

205640640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23827 (or 23811 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 27.

The square root of 205640640 is about 14340.1757311408. The cubic root of 205640640 is about 590.2504347163.

The spelling of 205640640 in words is "two hundred five million, six hundred forty thousand, six hundred forty".