21906917 has 2 divisors, whose sum is σ = 21906918. Its totient is φ = 21906916.

The previous prime is 21906889. The next prime is 21906949. The reversal of 21906917 is 71960912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14145121 + 7761796 = 3761^2 + 2786^2 .

It is a cyclic number.

It is not a de Polignac number, because 21906917 - 2¹² = 21902821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21906317) 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, 10953458 + 10953459.

It is an arithmetic number, because the mean of its divisors is an integer number (10953459).

Almost surely, 2^21906917 is an apocalyptic number.

It is an amenable number.

21906917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906917 is an equidigital number, since it uses as much as digits as its factorization.

21906917 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 21906917 is about 4680.4825605914. The cubic root of 21906917 is about 279.8081892105.

The spelling of 21906917 in words is "twenty-one million, nine hundred six thousand, nine hundred seventeen".