21580217 has 2 divisors, whose sum is σ = 21580218. Its totient is φ = 21580216.

The previous prime is 21580201. The next prime is 21580243. The reversal of 21580217 is 71208512.

It is an a-pointer prime, because the next prime (21580243) can be obtained adding 21580217 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21353641 + 226576 = 4621^2 + 476^2 .

It is a cyclic number.

It is not a de Polignac number, because 21580217 - 2⁴ = 21580201 is a prime.

It is not a weakly prime, because it can be changed into another prime (21580267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790108 + 10790109.

It is an arithmetic number, because the mean of its divisors is an integer number (10790109).

Almost surely, 2^21580217 is an apocalyptic number.

It is an amenable number.

21580217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21580217 is an equidigital number, since it uses as much as digits as its factorization.

21580217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21580217 is about 4645.4512159746. The cubic root of 21580217 is about 278.4102813135.

Adding to 21580217 its reverse (71208512), we get a palindrome (92788729).

The spelling of 21580217 in words is "twenty-one million, five hundred eighty thousand, two hundred seventeen".