21284518 has 4 divisors (see below), whose sum is σ = 31926780. Its totient is φ = 10642258.

The previous prime is 21284491. The next prime is 21284519. The reversal of 21284518 is 81548212.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21284518.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21284519) 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 as a sum of consecutive naturals, namely, 5321128 + ... + 5321131.

It is an arithmetic number, because the mean of its divisors is an integer number (7981695).

Almost surely, 2^21284518 is an apocalyptic number.

21284518 is a deficient number, since it is larger than the sum of its proper divisors (10642262).

21284518 is a wasteful number, since it uses less digits than its factorization.

21284518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10642261.

The product of its digits is 5120, while the sum is 31.

The square root of 21284518 is about 4613.5147122340. The cubic root of 21284518 is about 277.1328065478.

The spelling of 21284518 in words is "twenty-one million, two hundred eighty-four thousand, five hundred eighteen".