21497218 has 16 divisors (see below), whose sum is σ = 32994144. Its totient is φ = 10501920.

The previous prime is 21497213. The next prime is 21497257. The reversal of 21497218 is 81279412.

It is not an unprimeable number, because it can be changed into a prime (21497213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17773 + ... + 18943.

It is an arithmetic number, because the mean of its divisors is an integer number (2062134).

Almost surely, 2^21497218 is an apocalyptic number.

21497218 is a deficient number, since it is larger than the sum of its proper divisors (11496926).

21497218 is a wasteful number, since it uses less digits than its factorization.

21497218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1377.

The product of its digits is 8064, while the sum is 34.

The square root of 21497218 is about 4636.5092472678. The cubic root of 21497218 is about 278.0528943743.

The spelling of 21497218 in words is "twenty-one million, four hundred ninety-seven thousand, two hundred eighteen".