21927221 has 2 divisors, whose sum is σ = 21927222. Its totient is φ = 21927220.

The previous prime is 21927193. The next prime is 21927233. The reversal of 21927221 is 12272912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12348196 + 9579025 = 3514^2 + 3095^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21927221 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21927281) 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 as a sum of consecutive naturals, namely, 10963610 + 10963611.

It is an arithmetic number, because the mean of its divisors is an integer number (10963611).

Almost surely, 2^21927221 is an apocalyptic number.

It is an amenable number.

21927221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21927221 is an equidigital number, since it uses as much as digits as its factorization.

21927221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1008, while the sum is 26.

The square root of 21927221 is about 4682.6510653688. The cubic root of 21927221 is about 279.8946074439.

The spelling of 21927221 in words is "twenty-one million, nine hundred twenty-seven thousand, two hundred twenty-one".