21435421 has 4 divisors (see below), whose sum is σ = 24497632. Its totient is φ = 18373212.

The previous prime is 21435409. The next prime is 21435443. The reversal of 21435421 is 12453412.

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 a cyclic number.

It is not a de Polignac number, because 21435421 - 2⁵ = 21435389 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21435392 and 21435401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21435451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1531095 + ... + 1531108.

It is an arithmetic number, because the mean of its divisors is an integer number (6124408).

Almost surely, 2^21435421 is an apocalyptic number.

It is an amenable number.

21435421 is a deficient number, since it is larger than the sum of its proper divisors (3062211).

21435421 is an equidigital number, since it uses as much as digits as its factorization.

21435421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3062210.

The product of its digits is 960, while the sum is 22.

The square root of 21435421 is about 4629.8402780226. The cubic root of 21435421 is about 277.7862036496.

Adding to 21435421 its reverse (12453412), we get a palindrome (33888833).

Subtracting from 21435421 its reverse (12453412), we obtain a square (8982009 = 2997²).

The spelling of 21435421 in words is "twenty-one million, four hundred thirty-five thousand, four hundred twenty-one".