21328387 has 16 divisors (see below), whose sum is σ = 23379840. Its totient is φ = 19377792.

The previous prime is 21328381. The next prime is 21328399. The reversal of 21328387 is 78382312.

It is a cyclic number.

It is not a de Polignac number, because 21328387 - 2³ = 21328379 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21328381) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 119064 + ... + 119242.

It is an arithmetic number, because the mean of its divisors is an integer number (1461240).

Almost surely, 2^21328387 is an apocalyptic number.

21328387 is a deficient number, since it is larger than the sum of its proper divisors (2051453).

21328387 is a wasteful number, since it uses less digits than its factorization.

21328387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 402.

The product of its digits is 16128, while the sum is 34.

The square root of 21328387 is about 4618.2666661855. The cubic root of 21328387 is about 277.3230731085.

The spelling of 21328387 in words is "twenty-one million, three hundred twenty-eight thousand, three hundred eighty-seven".