21520307 has 2 divisors, whose sum is σ = 21520308. Its totient is φ = 21520306.

The previous prime is 21520297. The next prime is 21520361. The reversal of 21520307 is 70302512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21520307 - 2⁶ = 21520243 is a prime.

It is a super-2 number, since 2×21520307² = 926247226748498, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21520207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760153 + 10760154.

It is an arithmetic number, because the mean of its divisors is an integer number (10760154).

Almost surely, 2^21520307 is an apocalyptic number.

21520307 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520307 is an equidigital number, since it uses as much as digits as its factorization.

21520307 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21520307 is about 4638.9984910539. The cubic root of 21520307 is about 278.1524059515.

Adding to 21520307 its reverse (70302512), we get a palindrome (91822819).

The spelling of 21520307 in words is "twenty-one million, five hundred twenty thousand, three hundred seven".