21451421 has 4 divisors (see below), whose sum is σ = 21460992. Its totient is φ = 21441852.

The previous prime is 21451373. The next prime is 21451427. The reversal of 21451421 is 12415412.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21451421 - 2⁶ = 21451357 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21451393 and 21451402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21451427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 590 + ... + 6576.

It is an arithmetic number, because the mean of its divisors is an integer number (5365248).

Almost surely, 2^21451421 is an apocalyptic number.

It is an amenable number.

21451421 is a deficient number, since it is larger than the sum of its proper divisors (9571).

21451421 is an equidigital number, since it uses as much as digits as its factorization.

21451421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9570.

The product of its digits is 320, while the sum is 20.

The square root of 21451421 is about 4631.5678770801. The cubic root of 21451421 is about 277.8553022670.

Adding to 21451421 its reverse (12415412), we get a palindrome (33866833).

The spelling of 21451421 in words is "twenty-one million, four hundred fifty-one thousand, four hundred twenty-one".