21220344421 has 4 divisors (see below), whose sum is σ = 21620728332. Its totient is φ = 20819960512.

The previous prime is 21220344373. The next prime is 21220344463. The reversal of 21220344421 is 12444302212.

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 18910100196 + 2310244225 = 137514^2 + 48065^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220344421 - 2⁹ = 21220343909 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 (21220344221) 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, 200191876 + ... + 200191981.

It is an arithmetic number, because the mean of its divisors is an integer number (5405182083).

Almost surely, 2^21220344421 is an apocalyptic number.

It is an amenable number.

21220344421 is a deficient number, since it is larger than the sum of its proper divisors (400383911).

21220344421 is an equidigital number, since it uses as much as digits as its factorization.

21220344421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400383910.

The product of its (nonzero) digits is 3072, while the sum is 25.

Adding to 21220344421 its reverse (12444302212), we get a palindrome (33664646633).

The spelling of 21220344421 in words is "twenty-one billion, two hundred twenty million, three hundred forty-four thousand, four hundred twenty-one".