205591621797 has 16 divisors (see below), whose sum is σ = 304614671680. Its totient is φ = 137045560176.

The previous prime is 205591621793. The next prime is 205591621799. The reversal of 205591621797 is 797126195502.

It is a happy number.

205591621797 is a `hidden beast` number, since 2 + 0 + 5 + 5 + 9 + 1 + 621 + 7 + 9 + 7 = 666.

It is not a de Polignac number, because 205591621797 - 2² = 205591621793 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 (205591621793) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 185758 + ... + 667599.

It is an arithmetic number, because the mean of its divisors is an integer number (19038416980).

Almost surely, 2^205591621797 is an apocalyptic number.

205591621797 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

205591621797 is a deficient number, since it is larger than the sum of its proper divisors (99023049883).

205591621797 is an equidigital number, since it uses as much as digits as its factorization.

205591621797 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 862289 (or 862283 counting only the distinct ones).

The product of its (nonzero) digits is 2381400, while the sum is 54.

The spelling of 205591621797 in words is "two hundred five billion, five hundred ninety-one million, six hundred twenty-one thousand, seven hundred ninety-seven".