21756231065 has 8 divisors (see below), whose sum is σ = 26813085000. Its totient is φ = 16934579712.

The previous prime is 21756231059. The next prime is 21756231127. The reversal of 21756231065 is 56013265712.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 12471752329 + 9284478736 = 111677^2 + 96356^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21756231065 - 2⁸ = 21756230809 is a prime.

It is a Curzon number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 58800440 + ... + 58800809.

It is an arithmetic number, because the mean of its divisors is an integer number (3351635625).

Almost surely, 2^21756231065 is an apocalyptic number.

It is an amenable number.

21756231065 is a deficient number, since it is larger than the sum of its proper divisors (5056853935).

21756231065 is a wasteful number, since it uses less digits than its factorization.

21756231065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117601291.

The product of its (nonzero) digits is 75600, while the sum is 38.

Adding to 21756231065 its reverse (56013265712), we get a palindrome (77769496777).

The spelling of 21756231065 in words is "twenty-one billion, seven hundred fifty-six million, two hundred thirty-one thousand, sixty-five".