21250217 has 2 divisors, whose sum is σ = 21250218. Its totient is φ = 21250216.

The previous prime is 21250211. The next prime is 21250253. The reversal of 21250217 is 71205212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18524416 + 2725801 = 4304^2 + 1651^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21250217 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21250211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625108 + 10625109.

It is an arithmetic number, because the mean of its divisors is an integer number (10625109).

Almost surely, 2^21250217 is an apocalyptic number.

It is an amenable number.

21250217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21250217 is an equidigital number, since it uses as much as digits as its factorization.

21250217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 21250217 is about 4609.7957655410. The cubic root of 21250217 is about 276.9838556626.

Adding to 21250217 its reverse (71205212), we get a palindrome (92455429).

The spelling of 21250217 in words is "twenty-one million, two hundred fifty thousand, two hundred seventeen".