21420304221 has 4 divisors (see below), whose sum is σ = 28560405632. Its totient is φ = 14280202812.

The previous prime is 21420304207. The next prime is 21420304231. The reversal of 21420304221 is 12240302412.

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 not a de Polignac number, because 21420304221 - 2¹¹ = 21420302173 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 (21420304201) 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, 3570050701 + ... + 3570050706.

It is an arithmetic number, because the mean of its divisors is an integer number (7140101408).

Almost surely, 2^21420304221 is an apocalyptic number.

It is an amenable number.

21420304221 is a deficient number, since it is larger than the sum of its proper divisors (7140101411).

21420304221 is an equidigital number, since it uses as much as digits as its factorization.

21420304221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7140101410.

The product of its (nonzero) digits is 768, while the sum is 21.

Adding to 21420304221 its reverse (12240302412), we get a palindrome (33660606633).

The spelling of 21420304221 in words is "twenty-one billion, four hundred twenty million, three hundred four thousand, two hundred twenty-one".