21443421 has 8 divisors (see below), whose sum is σ = 29199744. Its totient is φ = 13991360.

The previous prime is 21443363. The next prime is 21443431. The reversal of 21443421 is 12434412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21443421 - 2¹¹ = 21441373 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21443431) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 75900 + ... + 76181.

It is an arithmetic number, because the mean of its divisors is an integer number (3649968).

Almost surely, 2^21443421 is an apocalyptic number.

It is an amenable number.

21443421 is a deficient number, since it is larger than the sum of its proper divisors (7756323).

21443421 is a wasteful number, since it uses less digits than its factorization.

21443421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152131.

The product of its digits is 768, while the sum is 21.

The square root of 21443421 is about 4630.7041581168. The cubic root of 21443421 is about 277.8207572548.

Adding to 21443421 its reverse (12434412), we get a palindrome (33877833).

Subtracting from 21443421 its reverse (12434412), we obtain a palindrome (9009009).

It can be divided in two parts, 2144 and 3421, that added together give a triangular number (5565 = T₁₀₅).

The spelling of 21443421 in words is "twenty-one million, four hundred forty-three thousand, four hundred twenty-one".