21024421 has 4 divisors (see below), whose sum is σ = 22935744. Its totient is φ = 19113100.

The previous prime is 21024413. The next prime is 21024433. The reversal of 21024421 is 12442012.

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 21024421 - 2³ = 21024413 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21024395 and 21024404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21024221) 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, 955645 + ... + 955666.

It is an arithmetic number, because the mean of its divisors is an integer number (5733936).

Almost surely, 2^21024421 is an apocalyptic number.

It is an amenable number.

21024421 is a deficient number, since it is larger than the sum of its proper divisors (1911323).

21024421 is a wasteful number, since it uses less digits than its factorization.

21024421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1911322.

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21024421 is about 4585.2394703003. The cubic root of 21024421 is about 275.9993217445. Note that the first 3 decimals are identical.

Adding to 21024421 its reverse (12442012), we get a palindrome (33466433).

The spelling of 21024421 in words is "twenty-one million, twenty-four thousand, four hundred twenty-one".