21257017 has 2 divisors, whose sum is σ = 21257018. Its totient is φ = 21257016.

The previous prime is 21257011. The next prime is 21257053. The reversal of 21257017 is 71075212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16842816 + 4414201 = 4104^2 + 2101^2 .

It is a cyclic number.

It is not a de Polignac number, because 21257017 - 2¹⁵ = 21224249 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21256982 and 21257000.

It is not a weakly prime, because it can be changed into another prime (21257011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628508 + 10628509.

It is an arithmetic number, because the mean of its divisors is an integer number (10628509).

Almost surely, 2^21257017 is an apocalyptic number.

It is an amenable number.

21257017 is a deficient number, since it is larger than the sum of its proper divisors (1).

21257017 is an equidigital number, since it uses as much as digits as its factorization.

21257017 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21257017 is about 4610.5332663370. The cubic root of 21257017 is about 277.0133971547.

The spelling of 21257017 in words is "twenty-one million, two hundred fifty-seven thousand, seventeen".