205640521 has 4 divisors (see below), whose sum is σ = 205673344. Its totient is φ = 205607700.

The previous prime is 205640509. The next prime is 205640527. The reversal of 205640521 is 125046502.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205640521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205640527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3765 + ... + 20626.

It is an arithmetic number, because the mean of its divisors is an integer number (51418336).

Almost surely, 2^205640521 is an apocalyptic number.

It is an amenable number.

205640521 is a deficient number, since it is larger than the sum of its proper divisors (32823).

205640521 is an equidigital number, since it uses as much as digits as its factorization.

205640521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32822.

The product of its (nonzero) digits is 2400, while the sum is 25.

The square root of 205640521 is about 14340.1715819581. The cubic root of 205640521 is about 590.2503208610.

The spelling of 205640521 in words is "two hundred five million, six hundred forty thousand, five hundred twenty-one".