21218097 has 4 divisors (see below), whose sum is σ = 28290800. Its totient is φ = 14145396.

The previous prime is 21218089. The next prime is 21218143. The reversal of 21218097 is 79081212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21218097 - 2³ = 21218089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21210097) 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 3 ways as a sum of consecutive naturals, for example, 3536347 + ... + 3536352.

It is an arithmetic number, because the mean of its divisors is an integer number (7072700).

Almost surely, 2^21218097 is an apocalyptic number.

It is an amenable number.

21218097 is a deficient number, since it is larger than the sum of its proper divisors (7072703).

21218097 is an equidigital number, since it uses as much as digits as its factorization.

21218097 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7072702.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21218097 is about 4606.3105626955. The cubic root of 21218097 is about 276.8442303007.

The spelling of 21218097 in words is "twenty-one million, two hundred eighteen thousand, ninety-seven".