21428447 has 4 divisors (see below), whose sum is σ = 22556280. Its totient is φ = 20300616.

The previous prime is 21428431. The next prime is 21428453. The reversal of 21428447 is 74482412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21428447 - 2⁴ = 21428431 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428497) 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, 563888 + ... + 563925.

It is an arithmetic number, because the mean of its divisors is an integer number (5639070).

Almost surely, 2^21428447 is an apocalyptic number.

21428447 is a deficient number, since it is larger than the sum of its proper divisors (1127833).

21428447 is a wasteful number, since it uses less digits than its factorization.

21428447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127832.

The product of its digits is 14336, while the sum is 32.

The square root of 21428447 is about 4629.0870590215. The cubic root of 21428447 is about 277.7560745295.

The spelling of 21428447 in words is "twenty-one million, four hundred twenty-eight thousand, four hundred forty-seven".