21312100213 has 4 divisors (see below), whose sum is σ = 21387944268. Its totient is φ = 21236256160.

The previous prime is 21312100189. The next prime is 21312100217. The reversal of 21312100213 is 31200121312.

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 14172188209 + 7139912004 = 119047^2 + 84498^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312100213 - 2²⁹ = 20775229301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312100217) 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, 37921606 + ... + 37922167.

It is an arithmetic number, because the mean of its divisors is an integer number (5346986067).

Almost surely, 2^21312100213 is an apocalyptic number.

It is an amenable number.

21312100213 is a deficient number, since it is larger than the sum of its proper divisors (75844055).

21312100213 is an equidigital number, since it uses as much as digits as its factorization.

21312100213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75844054.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21312100213 its reverse (31200121312), we get a palindrome (52512221525).

The spelling of 21312100213 in words is "twenty-one billion, three hundred twelve million, one hundred thousand, two hundred thirteen".