21222287 has 4 divisors (see below), whose sum is σ = 21954120. Its totient is φ = 20490456.

The previous prime is 21222269. The next prime is 21222293. The reversal of 21222287 is 78222212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21222287 - 2¹² = 21218191 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21222587) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 365873 + ... + 365930.

It is an arithmetic number, because the mean of its divisors is an integer number (5488530).

Almost surely, 2^21222287 is an apocalyptic number.

21222287 is a deficient number, since it is larger than the sum of its proper divisors (731833).

21222287 is an equidigital number, since it uses as much as digits as its factorization.

21222287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731832.

The product of its digits is 1792, while the sum is 26.

The square root of 21222287 is about 4606.7653510896. The cubic root of 21222287 is about 276.8624521827.

Adding to 21222287 its reverse (78222212), we get a palindrome (99444499).

The spelling of 21222287 in words is "twenty-one million, two hundred twenty-two thousand, two hundred eighty-seven".