21212323309 has 4 divisors (see below), whose sum is σ = 21212645404. Its totient is φ = 21212001216.

The previous prime is 21212323271. The next prime is 21212323333. The reversal of 21212323309 is 90332321212.

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 7940592100 + 13271731209 = 89110^2 + 115203^2 .

It is a cyclic number.

It is not a de Polignac number, because 21212323309 - 2²¹ = 21210226157 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 (21212323399) 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, 22572 + ... + 207205.

It is an arithmetic number, because the mean of its divisors is an integer number (5303161351).

Almost surely, 2^21212323309 is an apocalyptic number.

It is an amenable number.

21212323309 is a deficient number, since it is larger than the sum of its proper divisors (322095).

21212323309 is an equidigital number, since it uses as much as digits as its factorization.

21212323309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322094.

The product of its (nonzero) digits is 3888, while the sum is 28.

The spelling of 21212323309 in words is "twenty-one billion, two hundred twelve million, three hundred twenty-three thousand, three hundred nine".