21384518 has 8 divisors (see below), whose sum is σ = 32097648. Its totient is φ = 10685304.

The previous prime is 21384511. The next prime is 21384529. The reversal of 21384518 is 81548312.

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

It is a super-2 number, since 2×21384518² = 914595220184648, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21384511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2255 + ... + 6917.

It is an arithmetic number, because the mean of its divisors is an integer number (4012206).

Almost surely, 2^21384518 is an apocalyptic number.

21384518 is a deficient number, since it is larger than the sum of its proper divisors (10713130).

21384518 is a wasteful number, since it uses less digits than its factorization.

21384518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6958.

The product of its digits is 7680, while the sum is 32.

The square root of 21384518 is about 4624.3397366543. The cubic root of 21384518 is about 277.5661417428.

The spelling of 21384518 in words is "twenty-one million, three hundred eighty-four thousand, five hundred eighteen".