21212120213 has 4 divisors (see below), whose sum is σ = 21228106560. Its totient is φ = 21196133868.

The previous prime is 21212120183. The next prime is 21212120257. The reversal of 21212120213 is 31202121212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21212120213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21212120191 and 21212120200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212120273) 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, 7991183 + ... + 7993836.

It is an arithmetic number, because the mean of its divisors is an integer number (5307026640).

Almost surely, 2^21212120213 is an apocalyptic number.

It is an amenable number.

21212120213 is a deficient number, since it is larger than the sum of its proper divisors (15986347).

21212120213 is a wasteful number, since it uses less digits than its factorization.

21212120213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15986346.

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

Adding to 21212120213 its reverse (31202121212), we get a palindrome (52414241425).

Subtracting 21212120213 from its reverse (31202121212), we obtain a palindrome (9990000999).

The spelling of 21212120213 in words is "twenty-one billion, two hundred twelve million, one hundred twenty thousand, two hundred thirteen".