205807157021 has 4 divisors (see below), whose sum is σ = 205808209344. Its totient is φ = 205806104700.

The previous prime is 205807157009. The next prime is 205807157077. The reversal of 205807157021 is 120751708502.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 205807157021 - 2¹⁰ = 205807155997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (205807157221) 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, 136715 + ... + 655976.

It is an arithmetic number, because the mean of its divisors is an integer number (51452052336).

Almost surely, 2^205807157021 is an apocalyptic number.

It is an amenable number.

205807157021 is a deficient number, since it is larger than the sum of its proper divisors (1052323).

205807157021 is an equidigital number, since it uses as much as digits as its factorization.

205807157021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1052322.

The product of its (nonzero) digits is 39200, while the sum is 38.

The spelling of 205807157021 in words is "two hundred five billion, eight hundred seven million, one hundred fifty-seven thousand, twenty-one".