21012221121 has 16 divisors (see below), whose sum is σ = 29045026560. Its totient is φ = 13495870080.

The previous prime is 21012221059. The next prime is 21012221171. The reversal of 21012221121 is 12112221012.

It is not a de Polignac number, because 21012221121 - 2⁶ = 21012221057 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21012221121.

It is not an unprimeable number, because it can be changed into a prime (21012221171) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 220540 + ... + 301101.

It is an arithmetic number, because the mean of its divisors is an integer number (1815314160).

Almost surely, 2^21012221121 is an apocalyptic number.

It is an amenable number.

21012221121 is a deficient number, since it is larger than the sum of its proper divisors (8032805439).

21012221121 is a wasteful number, since it uses less digits than its factorization.

21012221121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522136.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21012221121 its reverse (12112221012), we get a palindrome (33124442133).

It can be divided in two parts, 2101 and 2221121, that added together give a palindrome (2223222).

The spelling of 21012221121 in words is "twenty-one billion, twelve million, two hundred twenty-one thousand, one hundred twenty-one".