205566650021 has 8 divisors (see below), whose sum is σ = 207623178840. Its totient is φ = 203513223168.

The previous prime is 205566649999. The next prime is 205566650117. The reversal of 205566650021 is 120056665502.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 4603622500 + 200963027521 = 67850^2 + 448289^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-205566650021 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 (205566650221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 642176 + ... + 907481.

It is an arithmetic number, because the mean of its divisors is an integer number (25952897355).

Almost surely, 2^205566650021 is an apocalyptic number.

It is an amenable number.

205566650021 is a deficient number, since it is larger than the sum of its proper divisors (2056528819).

205566650021 is a wasteful number, since it uses less digits than its factorization.

205566650021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1550983.

The product of its (nonzero) digits is 108000, while the sum is 38.

The spelling of 205566650021 in words is "two hundred five billion, five hundred sixty-six million, six hundred fifty thousand, twenty-one".