21212023121 has 4 divisors (see below), whose sum is σ = 21231360612. Its totient is φ = 21192685632.

The previous prime is 21212023087. The next prime is 21212023123. The reversal of 21212023121 is 12132021212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3336333121 + 17875690000 = 57761^2 + 133700^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21212023121 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21212023121.

It is not an unprimeable number, because it can be changed into a prime (21212023123) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9667100 + ... + 9669293.

It is an arithmetic number, because the mean of its divisors is an integer number (5307840153).

Almost surely, 2^21212023121 is an apocalyptic number.

It is an amenable number.

21212023121 is a deficient number, since it is larger than the sum of its proper divisors (19337491).

21212023121 is a wasteful number, since it uses less digits than its factorization.

21212023121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19337490.

The product of its (nonzero) digits is 96, while the sum is 17.

Adding to 21212023121 its reverse (12132021212), we get a palindrome (33344044333).

The spelling of 21212023121 in words is "twenty-one billion, two hundred twelve million, twenty-three thousand, one hundred twenty-one".