205640551 has 12 divisors (see below), whose sum is σ = 221106312. Its totient is φ = 191189888.

The previous prime is 205640549. The next prime is 205640563. The reversal of 205640551 is 155046502.

205640551 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 205640551 - 2¹ = 205640549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205640531) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 19701 + ... + 28273.

It is an arithmetic number, because the mean of its divisors is an integer number (18425526).

Almost surely, 2^205640551 is an apocalyptic number.

205640551 is a deficient number, since it is larger than the sum of its proper divisors (15465761).

205640551 is an equidigital number, since it uses as much as digits as its factorization.

205640551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8690 (or 8673 counting only the distinct ones).

The product of its (nonzero) digits is 6000, while the sum is 28.

The square root of 205640551 is about 14340.1726279707. The cubic root of 205640551 is about 590.2503495640.

The spelling of 205640551 in words is "two hundred five million, six hundred forty thousand, five hundred fifty-one".