21953221 has 2 divisors, whose sum is σ = 21953222. Its totient is φ = 21953220.

The previous prime is 21953167. The next prime is 21953233. The reversal of 21953221 is 12235912.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21288996 + 664225 = 4614^2 + 815^2 .

It is a cyclic number.

It is not a de Polignac number, because 21953221 - 2¹³ = 21945029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21953621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10976610 + 10976611.

It is an arithmetic number, because the mean of its divisors is an integer number (10976611).

Almost surely, 2^21953221 is an apocalyptic number.

It is an amenable number.

21953221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21953221 is an equidigital number, since it uses as much as digits as its factorization.

21953221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1080, while the sum is 25.

The square root of 21953221 is about 4685.4264480408. The cubic root of 21953221 is about 280.0051912303.

The spelling of 21953221 in words is "twenty-one million, nine hundred fifty-three thousand, two hundred twenty-one".