21440917 has 2 divisors, whose sum is σ = 21440918. Its totient is φ = 21440916.

The previous prime is 21440891. The next prime is 21440941. The reversal of 21440917 is 71904412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20711601 + 729316 = 4551^2 + 854^2 .

It is a cyclic number.

It is not a de Polignac number, because 21440917 - 2¹¹ = 21438869 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21440017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10720458 + 10720459.

It is an arithmetic number, because the mean of its divisors is an integer number (10720459).

Almost surely, 2^21440917 is an apocalyptic number.

It is an amenable number.

21440917 is a deficient number, since it is larger than the sum of its proper divisors (1).

21440917 is an equidigital number, since it uses as much as digits as its factorization.

21440917 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 28.

The square root of 21440917 is about 4630.4337809756. The cubic root of 21440917 is about 277.8099429005.

The spelling of 21440917 in words is "twenty-one million, four hundred forty thousand, nine hundred seventeen".