205878991 has 4 divisors (see below), whose sum is σ = 205961400. Its totient is φ = 205796584.

The previous prime is 205878949. The next prime is 205878997. The reversal of 205878991 is 199878502.

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 205878991 - 2⁹ = 205878479 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 (205878997) 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, 37336 + ... + 42493.

It is an arithmetic number, because the mean of its divisors is an integer number (51490350).

Almost surely, 2^205878991 is an apocalyptic number.

205878991 is a deficient number, since it is larger than the sum of its proper divisors (82409).

205878991 is an equidigital number, since it uses as much as digits as its factorization.

205878991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82408.

The product of its (nonzero) digits is 362880, while the sum is 49.

The square root of 205878991 is about 14348.4839268823. The cubic root of 205878991 is about 590.4783929987.

The spelling of 205878991 in words is "two hundred five million, eight hundred seventy-eight thousand, nine hundred ninety-one".