21384427 has 4 divisors (see below), whose sum is σ = 21596256. Its totient is φ = 21172600.

The previous prime is 21384421. The next prime is 21384449. The reversal of 21384427 is 72448312.

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 21384427 - 2⁷ = 21384299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21384421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105763 + ... + 105964.

It is an arithmetic number, because the mean of its divisors is an integer number (5399064).

Almost surely, 2^21384427 is an apocalyptic number.

21384427 is a deficient number, since it is larger than the sum of its proper divisors (211829).

21384427 is a wasteful number, since it uses less digits than its factorization.

21384427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211828.

The product of its digits is 10752, while the sum is 31.

The square root of 21384427 is about 4624.3298974014. The cubic root of 21384427 is about 277.5657480225.

The spelling of 21384427 in words is "twenty-one million, three hundred eighty-four thousand, four hundred twenty-seven".