21766765 has 4 divisors (see below), whose sum is σ = 26120124. Its totient is φ = 17413408.

The previous prime is 21766757. The next prime is 21766831. The reversal of 21766765 is 56766712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 14891881 + 6874884 = 3859^2 + 2622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21766765 - 2³ = 21766757 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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2176672 + ... + 2176681.

It is an arithmetic number, because the mean of its divisors is an integer number (6530031).

Almost surely, 2^21766765 is an apocalyptic number.

It is an amenable number.

21766765 is a deficient number, since it is larger than the sum of its proper divisors (4353359).

21766765 is an equidigital number, since it uses as much as digits as its factorization.

21766765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4353358.

The product of its digits is 105840, while the sum is 40.

The square root of 21766765 is about 4665.4865769821. The cubic root of 21766765 is about 279.2102105786.

The spelling of 21766765 in words is "twenty-one million, seven hundred sixty-six thousand, seven hundred sixty-five".