21320805 has 48 divisors (see below), whose sum is σ = 39759552. Its totient is φ = 9715200.

The previous prime is 21320801. The next prime is 21320813. The reversal of 21320805 is 50802312.

It is not a de Polignac number, because 21320805 - 2² = 21320801 is a prime.

It is a plaindrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320801) 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 in 47 ways as a sum of consecutive naturals, for example, 30510 + ... + 31200.

It is an arithmetic number, because the mean of its divisors is an integer number (828324).

Almost surely, 2^21320805 is an apocalyptic number.

It is an amenable number.

21320805 is a deficient number, since it is larger than the sum of its proper divisors (18438747).

21320805 is a wasteful number, since it uses less digits than its factorization.

21320805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 738 (or 727 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21320805 is about 4617.4457224747. The cubic root of 21320805 is about 277.2902074766.

The spelling of 21320805 in words is "twenty-one million, three hundred twenty thousand, eight hundred five".