21505007 has 2 divisors, whose sum is σ = 21505008. Its totient is φ = 21505006.

The previous prime is 21504971. The next prime is 21505009. The reversal of 21505007 is 70050512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21505007 - 2¹⁶ = 21439471 is a prime.

Together with 21505009, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21505007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21505009) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752503 + 10752504.

It is an arithmetic number, because the mean of its divisors is an integer number (10752504).

Almost surely, 2^21505007 is an apocalyptic number.

21505007 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505007 is an equidigital number, since it uses as much as digits as its factorization.

21505007 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 350, while the sum is 20.

The square root of 21505007 is about 4637.3491350124. The cubic root of 21505007 is about 278.0864722459.

Adding to 21505007 its reverse (70050512), we get a palindrome (91555519).

The spelling of 21505007 in words is "twenty-one million, five hundred five thousand, seven".