21331217 has 2 divisors, whose sum is σ = 21331218. Its totient is φ = 21331216.

The previous prime is 21331201. The next prime is 21331267. The reversal of 21331217 is 71213312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16128256 + 5202961 = 4016^2 + 2281^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331217 - 2⁴ = 21331201 is a prime.

It is not a weakly prime, because it can be changed into another prime (21331267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665608 + 10665609.

It is an arithmetic number, because the mean of its divisors is an integer number (10665609).

Almost surely, 2^21331217 is an apocalyptic number.

It is an amenable number.

21331217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331217 is an equidigital number, since it uses as much as digits as its factorization.

21331217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 252, while the sum is 20.

The square root of 21331217 is about 4618.5730480312. The cubic root of 21331217 is about 277.3353382896.

Adding to 21331217 its reverse (71213312), we get a palindrome (92544529).

The spelling of 21331217 in words is "twenty-one million, three hundred thirty-one thousand, two hundred seventeen".