21210120021 has 16 divisors (see below), whose sum is σ = 29449100160. Its totient is φ = 13562068800.

The previous prime is 21210120017. The next prime is 21210120037. The reversal of 21210120021 is 12002101212.

It is not a de Polignac number, because 21210120021 - 2² = 21210120017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21210119979 and 21210120006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210120011) 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 15 ways as a sum of consecutive naturals, for example, 794130 + ... + 820403.

It is an arithmetic number, because the mean of its divisors is an integer number (1840568760).

Almost surely, 2^21210120021 is an apocalyptic number.

It is an amenable number.

21210120021 is a deficient number, since it is larger than the sum of its proper divisors (8238980139).

21210120021 is a wasteful number, since it uses less digits than its factorization.

21210120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1614716.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21210120021 its reverse (12002101212), we get a palindrome (33212221233).

The spelling of 21210120021 in words is "twenty-one billion, two hundred ten million, one hundred twenty thousand, twenty-one".