21222391 has 2 divisors, whose sum is σ = 21222392. Its totient is φ = 21222390.

The previous prime is 21222371. The next prime is 21222401. The reversal of 21222391 is 19322212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21222391 - 2¹⁷ = 21091319 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21222361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10611195 + 10611196.

It is an arithmetic number, because the mean of its divisors is an integer number (10611196).

Almost surely, 2^21222391 is an apocalyptic number.

21222391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21222391 is an equidigital number, since it uses as much as digits as its factorization.

21222391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 22.

The square root of 21222391 is about 4606.7766388224. The cubic root of 21222391 is about 276.8629044376.

The spelling of 21222391 in words is "twenty-one million, two hundred twenty-two thousand, three hundred ninety-one".