21210212122221 has 16 divisors (see below), whose sum is σ = 28299137920128. Its totient is φ = 14130717004800.

The previous prime is 21210212122159. The next prime is 21210212122277. The reversal of 21210212122221 is 12222121201212.

It is not a de Polignac number, because 21210212122221 - 2⁷ = 21210212122093 is a prime.

It is a super-2 number, since 2×21210212122221² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210212122621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26881981 + ... + 27659741.

It is an arithmetic number, because the mean of its divisors is an integer number (1768696120008).

Almost surely, 2^{21210212122221} is an apocalyptic number.

It is an amenable number.

21210212122221 is a deficient number, since it is larger than the sum of its proper divisors (7088925797907).

21210212122221 is a wasteful number, since it uses less digits than its factorization.

21210212122221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 783812.

The product of its (nonzero) digits is 256, while the sum is 21.

Adding to 21210212122221 its reverse (12222121201212), we get a palindrome (33432333323433).

The spelling of 21210212122221 in words is "twenty-one trillion, two hundred ten billion, two hundred twelve million, one hundred twenty-two thousand, two hundred twenty-one".