21381307 has 2 divisors, whose sum is σ = 21381308. Its totient is φ = 21381306.

The previous prime is 21381281. The next prime is 21381317. The reversal of 21381307 is 70318312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21381307 - 2¹⁵ = 21348539 is a prime.

It is not a weakly prime, because it can be changed into another prime (21381317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10690653 + 10690654.

It is an arithmetic number, because the mean of its divisors is an integer number (10690654).

Almost surely, 2^21381307 is an apocalyptic number.

21381307 is a deficient number, since it is larger than the sum of its proper divisors (1).

21381307 is an equidigital number, since it uses as much as digits as its factorization.

21381307 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21381307 is about 4623.9925389213. The cubic root of 21381307 is about 277.5522483661.

Adding to 21381307 its reverse (70318312), we get a palindrome (91699619).

The spelling of 21381307 in words is "twenty-one million, three hundred eighty-one thousand, three hundred seven".