21160765 has 8 divisors (see below), whose sum is σ = 25420248. Its totient is φ = 16910400.

The previous prime is 21160747. The next prime is 21160771. The reversal of 21160765 is 56706112.

21160765 is a nontrivial binomial coefficient, being equal to C(6506, 2).

It can be written as a sum of positive squares in 4 ways, for example, as 1923769 + 19236996 = 1387^2 + 4386^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-21160765 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4879 + ... + 8131.

It is an arithmetic number, because the mean of its divisors is an integer number (3177531).

Almost surely, 2^21160765 is an apocalyptic number.

21160765 is the 6505-th triangular number and also the 3253-rd hexagonal number.

21160765 is the 2169-th centered nonagonal number.

It is an amenable number.

21160765 is a deficient number, since it is larger than the sum of its proper divisors (4259483).

21160765 is a wasteful number, since it uses less digits than its factorization.

21160765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4559.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21160765 is about 4600.0831514224. The cubic root of 21160765 is about 276.5946579585.

Adding to 21160765 its reverse (56706112), we get a palindrome (77866877).

The spelling of 21160765 in words is "twenty-one million, one hundred sixty thousand, seven hundred sixty-five".