21217307 has 2 divisors, whose sum is σ = 21217308. Its totient is φ = 21217306.

The previous prime is 21217289. The next prime is 21217337. The reversal of 21217307 is 70371212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21217307 - 2¹⁴ = 21200923 is a prime.

It is equal to p_1342805 and since 21217307 and 1342805 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21217337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10608653 + 10608654.

It is an arithmetic number, because the mean of its divisors is an integer number (10608654).

Almost surely, 2^21217307 is an apocalyptic number.

21217307 is a deficient number, since it is larger than the sum of its proper divisors (1).

21217307 is an equidigital number, since it uses as much as digits as its factorization.

21217307 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 588, while the sum is 23.

The square root of 21217307 is about 4606.2248099718. The cubic root of 21217307 is about 276.8407944026.

Adding to 21217307 its reverse (70371212), we get a palindrome (91588519).

The spelling of 21217307 in words is "twenty-one million, two hundred seventeen thousand, three hundred seven".