21212120105 has 32 divisors (see below), whose sum is σ = 28246496256. Its totient is φ = 15162840000.

The previous prime is 21212120099. The next prime is 21212120123. The reversal of 21212120105 is 50102121212.

It is not a de Polignac number, because 21212120105 - 2⁴ = 21212120089 is a prime.

It is a super-2 number, since 2×21212120105² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1284350 + ... + 1300760.

It is an arithmetic number, because the mean of its divisors is an integer number (882703008).

Almost surely, 2^21212120105 is an apocalyptic number.

It is an amenable number.

21212120105 is a deficient number, since it is larger than the sum of its proper divisors (7034376151).

21212120105 is a wasteful number, since it uses less digits than its factorization.

21212120105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16829.

The product of its (nonzero) digits is 80, while the sum is 17.

Adding to 21212120105 its reverse (50102121212), we get a palindrome (71314241317).

The spelling of 21212120105 in words is "twenty-one billion, two hundred twelve million, one hundred twenty thousand, one hundred five".