21191617 has 2 divisors, whose sum is σ = 21191618. Its totient is φ = 21191616.

The previous prime is 21191603. The next prime is 21191623. The reversal of 21191617 is 71619112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11943936 + 9247681 = 3456^2 + 3041^2 .

It is a cyclic number.

It is not a de Polignac number, because 21191617 - 2²³ = 12803009 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21191657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10595808 + 10595809.

It is an arithmetic number, because the mean of its divisors is an integer number (10595809).

Almost surely, 2^21191617 is an apocalyptic number.

It is an amenable number.

21191617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21191617 is an equidigital number, since it uses as much as digits as its factorization.

21191617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 756, while the sum is 28.

The square root of 21191617 is about 4603.4353476507. The cubic root of 21191617 is about 276.7290159636.

The spelling of 21191617 in words is "twenty-one million, one hundred ninety-one thousand, six hundred seventeen".