21222251 has 2 divisors, whose sum is σ = 21222252. Its totient is φ = 21222250.

The previous prime is 21222211. The next prime is 21222269. The reversal of 21222251 is 15222212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21222251 - 2¹⁴ = 21205867 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21222211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10611125 + 10611126.

It is an arithmetic number, because the mean of its divisors is an integer number (10611126).

Almost surely, 2^21222251 is an apocalyptic number.

21222251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21222251 is an equidigital number, since it uses as much as digits as its factorization.

21222251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 160, while the sum is 17.

The square root of 21222251 is about 4606.7614437911. The cubic root of 21222251 is about 276.8622956326.

Adding to 21222251 its reverse (15222212), we get a palindrome (36444463).

The spelling of 21222251 in words is "twenty-one million, two hundred twenty-two thousand, two hundred fifty-one".