21663349 has 2 divisors, whose sum is σ = 21663350. Its totient is φ = 21663348.

The previous prime is 21663337. The next prime is 21663359. The reversal of 21663349 is 94336612.

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., 20088324 + 1575025 = 4482^2 + 1255^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663349 - 2¹⁹ = 21139061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21663329) 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, 10831674 + 10831675.

It is an arithmetic number, because the mean of its divisors is an integer number (10831675).

Almost surely, 2^21663349 is an apocalyptic number.

It is an amenable number.

21663349 is a deficient number, since it is larger than the sum of its proper divisors (1).

21663349 is an equidigital number, since it uses as much as digits as its factorization.

21663349 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 34.

The square root of 21663349 is about 4654.3902930459. The cubic root of 21663349 is about 278.7673235562.

The spelling of 21663349 in words is "twenty-one million, six hundred sixty-three thousand, three hundred forty-nine".