21908317 has 2 divisors, whose sum is σ = 21908318. Its totient is φ = 21908316.

The previous prime is 21908303. The next prime is 21908363. The reversal of 21908317 is 71380912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13734436 + 8173881 = 3706^2 + 2859^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21908317 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 (21908377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10954158 + 10954159.

It is an arithmetic number, because the mean of its divisors is an integer number (10954159).

Almost surely, 2^21908317 is an apocalyptic number.

It is an amenable number.

21908317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21908317 is an equidigital number, since it uses as much as digits as its factorization.

21908317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21908317 is about 4680.6321154306. The cubic root of 21908317 is about 279.8141496280.

The spelling of 21908317 in words is "twenty-one million, nine hundred eight thousand, three hundred seventeen".