21722218 has 16 divisors (see below), whose sum is σ = 38522880. Its totient is φ = 8988336.

The previous prime is 21722213. The next prime is 21722221. The reversal of 21722218 is 81222712.

It is a junction number, because it is equal to n+sod(n) for n = 21722192 and 21722201.

It is not an unprimeable number, because it can be changed into a prime (21722213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26346 + ... + 27157.

It is an arithmetic number, because the mean of its divisors is an integer number (2407680).

Almost surely, 2^21722218 is an apocalyptic number.

21722218 is a deficient number, since it is larger than the sum of its proper divisors (16800662).

21722218 is a wasteful number, since it uses less digits than its factorization.

21722218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53541.

The product of its digits is 896, while the sum is 25.

The square root of 21722218 is about 4660.7100317441. The cubic root of 21722218 is about 279.0196069690.

The spelling of 21722218 in words is "twenty-one million, seven hundred twenty-two thousand, two hundred eighteen".