21428421 has 8 divisors (see below), whose sum is σ = 32652864. Its totient is φ = 12244800.

The previous prime is 21428413. The next prime is 21428423. The reversal of 21428421 is 12482412.

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

It is not a de Polignac number, because 21428421 - 2³ = 21428413 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21428391 and 21428400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428423) 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 7 ways as a sum of consecutive naturals, for example, 510180 + ... + 510221.

It is an arithmetic number, because the mean of its divisors is an integer number (4081608).

Almost surely, 2^21428421 is an apocalyptic number.

21428421 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21428421 is a deficient number, since it is larger than the sum of its proper divisors (11224443).

21428421 is a wasteful number, since it uses less digits than its factorization.

21428421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1020411.

The product of its digits is 1024, while the sum is 24.

The square root of 21428421 is about 4629.0842506915. The cubic root of 21428421 is about 277.7559621919.

The spelling of 21428421 in words is "twenty-one million, four hundred twenty-eight thousand, four hundred twenty-one".