21428391 has 8 divisors (see below), whose sum is σ = 28629360. Its totient is φ = 14256512.

The previous prime is 21428389. The next prime is 21428401. The reversal of 21428391 is 19382412.

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 21428391 - 2¹ = 21428389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428191) 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, 5490 + ... + 8543.

It is an arithmetic number, because the mean of its divisors is an integer number (3578670).

Almost surely, 2^21428391 is an apocalyptic number.

21428391 is a deficient number, since it is larger than the sum of its proper divisors (7200969).

21428391 is a wasteful number, since it uses less digits than its factorization.

21428391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14545.

The product of its digits is 3456, while the sum is 30.

The square root of 21428391 is about 4629.0810103086. The cubic root of 21428391 is about 277.7558325715.

The spelling of 21428391 in words is "twenty-one million, four hundred twenty-eight thousand, three hundred ninety-one".