20997218 has 16 divisors (see below), whose sum is σ = 35544960. Its totient is φ = 9214800.

The previous prime is 20997217. The next prime is 20997253. The reversal of 20997218 is 81279902.

It is not an unprimeable number, because it can be changed into a prime (20997211) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15818 + ... + 17093.

It is an arithmetic number, because the mean of its divisors is an integer number (2221560).

Almost surely, 2^20997218 is an apocalyptic number.

20997218 is a deficient number, since it is larger than the sum of its proper divisors (14547742).

20997218 is a wasteful number, since it uses less digits than its factorization.

20997218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32953.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 20997218 is about 4582.2721438169. The cubic root of 20997218 is about 275.8802340413.

The spelling of 20997218 in words is "twenty million, nine hundred ninety-seven thousand, two hundred eighteen".