21045765 has 16 divisors (see below), whose sum is σ = 36263808. Its totient is φ = 10360896.

The previous prime is 21045763. The next prime is 21045767. The reversal of 21045765 is 56754012.

It is an interprime number because it is at equal distance from previous prime (21045763) and next prime (21045767).

It is not a de Polignac number, because 21045765 - 2¹ = 21045763 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21045763) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53769 + ... + 54158.

It is an arithmetic number, because the mean of its divisors is an integer number (2266488).

Almost surely, 2^21045765 is an apocalyptic number.

It is an amenable number.

21045765 is a deficient number, since it is larger than the sum of its proper divisors (15218043).

21045765 is a wasteful number, since it uses less digits than its factorization.

21045765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107948.

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 21045765 is about 4587.5663482940. The cubic root of 21045765 is about 276.0926883609.

Adding to 21045765 its reverse (56754012), we get a palindrome (77799777).

The spelling of 21045765 in words is "twenty-one million, forty-five thousand, seven hundred sixty-five".