21012120021 has 8 divisors (see below), whose sum is σ = 28018091520. Its totient is φ = 14007114272.

The previous prime is 21012119983. The next prime is 21012120047. The reversal of 21012120021 is 12002121012.

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

It is a cyclic number.

It is not a de Polignac number, because 21012120021 - 2⁹ = 21012119509 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21012119979 and 21012120006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012120061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 189045 + ... + 278858.

It is an arithmetic number, because the mean of its divisors is an integer number (3502261440).

Almost surely, 2^21012120021 is an apocalyptic number.

It is an amenable number.

21012120021 is a deficient number, since it is larger than the sum of its proper divisors (7005971499).

21012120021 is a wasteful number, since it uses less digits than its factorization.

21012120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 482875.

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

Adding to 21012120021 its reverse (12002121012), we get a palindrome (33014241033).

Subtracting from 21012120021 its reverse (12002121012), we obtain a palindrome (9009999009).

It can be divided in two parts, 21012 and 120021, that multiplied together give a palindrome (2521881252).

The spelling of 21012120021 in words is "twenty-one billion, twelve million, one hundred twenty thousand, twenty-one".