21428871 has 4 divisors (see below), whose sum is σ = 28571832. Its totient is φ = 14285912.

The previous prime is 21428861. The next prime is 21428887. The reversal of 21428871 is 17882412.

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 21428871 - 2⁶ = 21428807 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428831) 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, 3571476 + ... + 3571481.

It is an arithmetic number, because the mean of its divisors is an integer number (7142958).

Almost surely, 2^21428871 is an apocalyptic number.

21428871 is a deficient number, since it is larger than the sum of its proper divisors (7142961).

21428871 is an equidigital number, since it uses as much as digits as its factorization.

21428871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7142960.

The product of its digits is 7168, while the sum is 33.

The square root of 21428871 is about 4629.1328561622. The cubic root of 21428871 is about 277.7579064837.

The spelling of 21428871 in words is "twenty-one million, four hundred twenty-eight thousand, eight hundred seventy-one".