21020065 has 16 divisors (see below), whose sum is σ = 28040256. Its totient is φ = 14996800.

The previous prime is 21020059. The next prime is 21020081. The reversal of 21020065 is 56002012.

It is a happy number.

It is not a de Polignac number, because 21020065 - 2³ = 21020057 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 691 + ... + 6520.

It is an arithmetic number, because the mean of its divisors is an integer number (1752516).

Almost surely, 2^21020065 is an apocalyptic number.

It is an amenable number.

21020065 is a deficient number, since it is larger than the sum of its proper divisors (7020191).

21020065 is a wasteful number, since it uses less digits than its factorization.

21020065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7280.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21020065 is about 4584.7644432402. The cubic root of 21020065 is about 275.9802592126.

Adding to 21020065 its reverse (56002012), we get a palindrome (77022077).

The spelling of 21020065 in words is "twenty-one million, twenty thousand, sixty-five".