21424457 has 4 divisors (see below), whose sum is σ = 22552080. Its totient is φ = 20296836.

The previous prime is 21424451. The next prime is 21424489. The reversal of 21424457 is 75442412.

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 21424457 - 2²⁰ = 20375881 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21424451) 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, 563783 + ... + 563820.

It is an arithmetic number, because the mean of its divisors is an integer number (5638020).

Almost surely, 2^21424457 is an apocalyptic number.

It is an amenable number.

21424457 is a deficient number, since it is larger than the sum of its proper divisors (1127623).

21424457 is a wasteful number, since it uses less digits than its factorization.

21424457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127622.

The product of its digits is 8960, while the sum is 29.

The square root of 21424457 is about 4628.6560684501. The cubic root of 21424457 is about 277.7388339656.

Adding to 21424457 its reverse (75442412), we get a palindrome (96866869).

The spelling of 21424457 in words is "twenty-one million, four hundred twenty-four thousand, four hundred fifty-seven".