21428571 has 8 divisors (see below), whose sum is σ = 29813760. Its totient is φ = 13664552.

The previous prime is 21428549. The next prime is 21428579. The reversal of 21428571 is 17582412.

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

It is a cyclic number.

It is not a de Polignac number, because 21428571 - 2¹⁹ = 20904283 is a prime.

21428571 is a modest number, since divided by 428571 gives 21 as remainder.

It is not an unprimeable number, because it can be changed into a prime (21428579) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 155211 + ... + 155348.

It is an arithmetic number, because the mean of its divisors is an integer number (3726720).

Almost surely, 2^21428571 is an apocalyptic number.

21428571 is a deficient number, since it is larger than the sum of its proper divisors (8385189).

21428571 is a wasteful number, since it uses less digits than its factorization.

21428571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310585.

The product of its digits is 4480, while the sum is 30.

The square root of 21428571 is about 4629.1004525718. The cubic root of 21428571 is about 277.7566102922.

The spelling of 21428571 in words is "twenty-one million, four hundred twenty-eight thousand, five hundred seventy-one".