21331421 has 4 divisors (see below), whose sum is σ = 21391200. Its totient is φ = 21271644.

The previous prime is 21331399. The next prime is 21331451. The reversal of 21331421 is 12413312.

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 21331421 - 2¹⁴ = 21315037 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21331421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21331451) 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, 29351 + ... + 30068.

It is an arithmetic number, because the mean of its divisors is an integer number (5347800).

Almost surely, 2^21331421 is an apocalyptic number.

It is an amenable number.

21331421 is a deficient number, since it is larger than the sum of its proper divisors (59779).

21331421 is an equidigital number, since it uses as much as digits as its factorization.

21331421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59778.

The product of its digits is 144, while the sum is 17.

The square root of 21331421 is about 4618.5951327216. The cubic root of 21331421 is about 277.3362223809.

Adding to 21331421 its reverse (12413312), we get a palindrome (33744733).

The spelling of 21331421 in words is "twenty-one million, three hundred thirty-one thousand, four hundred twenty-one".