21756765 has 16 divisors (see below), whose sum is σ = 35468928. Its totient is φ = 11384256.

The previous prime is 21756733. The next prime is 21756769. The reversal of 21756765 is 56765712.

It is not a de Polignac number, because 21756765 - 2⁵ = 21756733 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 (21756769) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12889 + ... + 14478.

It is an arithmetic number, because the mean of its divisors is an integer number (2216808).

Almost surely, 2^21756765 is an apocalyptic number.

It is an amenable number.

21756765 is a deficient number, since it is larger than the sum of its proper divisors (13712163).

21756765 is a wasteful number, since it uses less digits than its factorization.

21756765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27428.

The product of its digits is 88200, while the sum is 39.

The square root of 21756765 is about 4664.4147542859. The cubic root of 21756765 is about 279.1674461501.

The spelling of 21756765 in words is "twenty-one million, seven hundred fifty-six thousand, seven hundred sixty-five".