21280471 has 4 divisors (see below), whose sum is σ = 21337000. Its totient is φ = 21223944.

The previous prime is 21280459. The next prime is 21280487. The reversal of 21280471 is 17408212.

It is a happy number.

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 21280471 - 2⁹ = 21279959 is a prime.

It is a super-3 number, since 3×21280471³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280771) 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, 27696 + ... + 28453.

It is an arithmetic number, because the mean of its divisors is an integer number (5334250).

Almost surely, 2^21280471 is an apocalyptic number.

21280471 is a deficient number, since it is larger than the sum of its proper divisors (56529).

21280471 is an equidigital number, since it uses as much as digits as its factorization.

21280471 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56528.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 21280471 is about 4613.0760886853. The cubic root of 21280471 is about 277.1152409232.

Adding to 21280471 its reverse (17408212), we get a palindrome (38688683).

The spelling of 21280471 in words is "twenty-one million, two hundred eighty thousand, four hundred seventy-one".