21210120205 has 8 divisors (see below), whose sum is σ = 26072928504. Its totient is φ = 16554240000.

The previous prime is 21210120163. The next prime is 21210120209. The reversal of 21210120205 is 50202101212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 844832356 + 20365287849 = 29066^2 + 142707^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-21210120205 is a prime.

It is a super-2 number, since 2×21210120205² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210120209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 51731796 + ... + 51732205.

It is an arithmetic number, because the mean of its divisors is an integer number (3259116063).

Almost surely, 2^21210120205 is an apocalyptic number.

It is an amenable number.

21210120205 is a deficient number, since it is larger than the sum of its proper divisors (4862808299).

21210120205 is a wasteful number, since it uses less digits than its factorization.

21210120205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103464047.

The product of its (nonzero) digits is 80, while the sum is 16.

Adding to 21210120205 its reverse (50202101212), we get a palindrome (71412221417).

The spelling of 21210120205 in words is "twenty-one billion, two hundred ten million, one hundred twenty thousand, two hundred five".