21251002205 has 8 divisors (see below), whose sum is σ = 25507275192. Its totient is φ = 16996753408.

The previous prime is 21251002147. The next prime is 21251002217. The reversal of 21251002205 is 50220015212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 5721107044 + 15529895161 = 75638^2 + 124619^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21251002205 - 2⁶ = 21251002141 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 482852 + ... + 525021.

It is an arithmetic number, because the mean of its divisors is an integer number (3188409399).

Almost surely, 2^21251002205 is an apocalyptic number.

It is an amenable number.

21251002205 is a deficient number, since it is larger than the sum of its proper divisors (4256272987).

21251002205 is a wasteful number, since it uses less digits than its factorization.

21251002205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1012095.

The product of its (nonzero) digits is 400, while the sum is 20.

Adding to 21251002205 its reverse (50220015212), we get a palindrome (71471017417).

The spelling of 21251002205 in words is "twenty-one billion, two hundred fifty-one million, two thousand, two hundred five".