21002065 has 16 divisors (see below), whose sum is σ = 28881792. Its totient is φ = 14361984.

The previous prime is 21002039. The next prime is 21002077. The reversal of 21002065 is 56020012.

It is a happy number.

It is not a de Polignac number, because 21002065 - 2¹³ = 20993873 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, 18597 + ... + 19693.

It is an arithmetic number, because the mean of its divisors is an integer number (1805112).

Almost surely, 2^21002065 is an apocalyptic number.

It is an amenable number.

21002065 is a deficient number, since it is larger than the sum of its proper divisors (7879727).

21002065 is a wasteful number, since it uses less digits than its factorization.

21002065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1656.

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

The square root of 21002065 is about 4582.8009993889. The cubic root of 21002065 is about 275.9014604821.

Adding to 21002065 its reverse (56020012), we get a palindrome (77022077).

The spelling of 21002065 in words is "twenty-one million, two thousand, sixty-five".