205640851 has 4 divisors (see below), whose sum is σ = 221459392. Its totient is φ = 189822312.

The previous prime is 205640849. The next prime is 205640867. The reversal of 205640851 is 158046502.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 205640851 - 2¹ = 205640849 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (205640881) 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, 7909251 + ... + 7909276.

It is an arithmetic number, because the mean of its divisors is an integer number (55364848).

Almost surely, 2^205640851 is an apocalyptic number.

205640851 is a deficient number, since it is larger than the sum of its proper divisors (15818541).

205640851 is a wasteful number, since it uses less digits than its factorization.

205640851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15818540.

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 205640851 is about 14340.1830880920. The cubic root of 205640851 is about 590.2506365940.

The spelling of 205640851 in words is "two hundred five million, six hundred forty thousand, eight hundred fifty-one".