21360421 has 4 divisors (see below), whose sum is σ = 21661344. Its totient is φ = 21059500.

The previous prime is 21360407. The next prime is 21360439. The reversal of 21360421 is 12406312.

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 21360421 - 2¹¹ = 21358373 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 (21360401) 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, 150355 + ... + 150496.

It is an arithmetic number, because the mean of its divisors is an integer number (5415336).

Almost surely, 2^21360421 is an apocalyptic number.

It is an amenable number.

21360421 is a deficient number, since it is larger than the sum of its proper divisors (300923).

21360421 is an equidigital number, since it uses as much as digits as its factorization.

21360421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300922.

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

The square root of 21360421 is about 4621.7335492215. The cubic root of 21360421 is about 277.4618447121.

Adding to 21360421 its reverse (12406312), we get a palindrome (33766733).

The spelling of 21360421 in words is "twenty-one million, three hundred sixty thousand, four hundred twenty-one".