21520207 has 2 divisors, whose sum is σ = 21520208. Its totient is φ = 21520206.

The previous prime is 21520193. The next prime is 21520229. The reversal of 21520207 is 70202512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21520207 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21520297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760103 + 10760104.

It is an arithmetic number, because the mean of its divisors is an integer number (10760104).

Almost surely, 2^21520207 is an apocalyptic number.

21520207 is a deficient number, since it is larger than the sum of its proper divisors (1).

21520207 is an equidigital number, since it uses as much as digits as its factorization.

21520207 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 21520207 is about 4638.9877128529. The cubic root of 21520207 is about 278.1519751137.

Adding to 21520207 its reverse (70202512), we get a palindrome (91722719).

The spelling of 21520207 in words is "twenty-one million, five hundred twenty thousand, two hundred seven".