21421435421 has 4 divisors (see below), whose sum is σ = 21449585244. Its totient is φ = 21393285600.

The previous prime is 21421435391. The next prime is 21421435499. The reversal of 21421435421 is 12453412412.

It is a happy number.

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 9202564900 + 12218870521 = 95930^2 + 110539^2 .

It is a cyclic number.

It is not a de Polignac number, because 21421435421 - 2³⁴ = 4241566237 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 (21421435121) 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, 14073770 + ... + 14075291.

It is an arithmetic number, because the mean of its divisors is an integer number (5362396311).

Almost surely, 2^21421435421 is an apocalyptic number.

It is an amenable number.

21421435421 is a deficient number, since it is larger than the sum of its proper divisors (28149823).

21421435421 is an equidigital number, since it uses as much as digits as its factorization.

21421435421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28149822.

The product of its digits is 7680, while the sum is 29.

Adding to 21421435421 its reverse (12453412412), we get a palindrome (33874847833).

The spelling of 21421435421 in words is "twenty-one billion, four hundred twenty-one million, four hundred thirty-five thousand, four hundred twenty-one".