21220312321 has 4 divisors (see below), whose sum is σ = 22852644052. Its totient is φ = 19587980592.

The previous prime is 21220312319. The next prime is 21220312343. The reversal of 21220312321 is 12321302212.

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 13460640400 + 7759671921 = 116020^2 + 88089^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220312321 - 2¹ = 21220312319 is a prime.

It is a super-3 number, since 3×21220312321³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21220312301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 816165846 + ... + 816165871.

It is an arithmetic number, because the mean of its divisors is an integer number (5713161013).

Almost surely, 2^21220312321 is an apocalyptic number.

It is an amenable number.

21220312321 is a deficient number, since it is larger than the sum of its proper divisors (1632331731).

21220312321 is a wasteful number, since it uses less digits than its factorization.

21220312321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1632331730.

The product of its (nonzero) digits is 288, while the sum is 19.

Adding to 21220312321 its reverse (12321302212), we get a palindrome (33541614533).

The spelling of 21220312321 in words is "twenty-one billion, two hundred twenty million, three hundred twelve thousand, three hundred twenty-one".