21320065 has 16 divisors (see below), whose sum is σ = 27686736. Its totient is φ = 15667200.

The previous prime is 21320059. The next prime is 21320081. The reversal of 21320065 is 56002312.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 2039184 + 19280881 = 1428^2 + 4391^2 .

It is not a de Polignac number, because 21320065 - 2⁷ = 21319937 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14985 + ... + 16345.

It is an arithmetic number, because the mean of its divisors is an integer number (1730421).

Almost surely, 2^21320065 is an apocalyptic number.

It is an amenable number.

21320065 is a deficient number, since it is larger than the sum of its proper divisors (6366671).

21320065 is a wasteful number, since it uses less digits than its factorization.

21320065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1620.

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21320065 is about 4617.3655908970. The cubic root of 21320065 is about 277.2869993875.

Adding to 21320065 its reverse (56002312), we get a palindrome (77322377).

The spelling of 21320065 in words is "twenty-one million, three hundred twenty thousand, sixty-five".