21218063 has 4 divisors (see below), whose sum is σ = 21234360. Its totient is φ = 21201768.

The previous prime is 21218059. The next prime is 21218069. The reversal of 21218063 is 36081212.

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 21218063 - 2² = 21218059 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218069) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6008 + ... + 8861.

It is an arithmetic number, because the mean of its divisors is an integer number (5308590).

Almost surely, 2^21218063 is an apocalyptic number.

21218063 is a deficient number, since it is larger than the sum of its proper divisors (16297).

21218063 is a wasteful number, since it uses less digits than its factorization.

21218063 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16296.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21218063 is about 4606.3068721048. The cubic root of 21218063 is about 276.8440824284.

Adding to 21218063 its reverse (36081212), we get a palindrome (57299275).

The spelling of 21218063 in words is "twenty-one million, two hundred eighteen thousand, sixty-three".