21121205211 has 12 divisors (see below), whose sum is σ = 31025499960. Its totient is φ = 13842145440.

The previous prime is 21121205159. The next prime is 21121205243. The reversal of 21121205211 is 11250212112.

21121205211 is a `hidden beast` number, since 2 + 1 + 121 + 20 + 521 + 1 = 666.

It is not a de Polignac number, because 21121205211 - 2¹⁰ = 21121204187 is a prime.

It is a super-2 number, since 2×21121205211² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21121205251) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 19887610 + ... + 19888671.

It is an arithmetic number, because the mean of its divisors is an integer number (2585458330).

Almost surely, 2^21121205211 is an apocalyptic number.

21121205211 is a deficient number, since it is larger than the sum of its proper divisors (9904294749).

21121205211 is a wasteful number, since it uses less digits than its factorization.

21121205211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39776346 (or 39776343 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

Adding to 21121205211 its reverse (11250212112), we get a palindrome (32371417323).

The spelling of 21121205211 in words is "twenty-one billion, one hundred twenty-one million, two hundred five thousand, two hundred eleven".