21218073 has 8 divisors (see below), whose sum is σ = 28824768. Its totient is φ = 13878384.

The previous prime is 21218069. The next prime is 21218083. The reversal of 21218073 is 37081212.

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

It is not a de Polignac number, because 21218073 - 2² = 21218069 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21218083) 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 7 ways as a sum of consecutive naturals, for example, 66565 + ... + 66882.

It is an arithmetic number, because the mean of its divisors is an integer number (3603096).

Almost surely, 2^21218073 is an apocalyptic number.

It is an amenable number.

21218073 is a deficient number, since it is larger than the sum of its proper divisors (7606695).

21218073 is a wasteful number, since it uses less digits than its factorization.

21218073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133503.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21218073 is about 4606.3079575730. The cubic root of 21218073 is about 276.8441259203.

Adding to 21218073 its reverse (37081212), we get a palindrome (58299285).

The spelling of 21218073 in words is "twenty-one million, two hundred eighteen thousand, seventy-three".