21986523765 has 20 divisors (see below), whose sum is σ = 39412880364. Its totient is φ = 11726145792.

The previous prime is 21986523751. The next prime is 21986523803. The reversal of 21986523765 is 56732568912.

21986523765 is a `hidden beast` number, since 21 + 98 + 6 + 523 + 7 + 6 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 17548565841 + 4437957924 = 132471^2 + 66618^2 .

It is not a de Polignac number, because 21986523765 - 2⁶ = 21986523701 is a prime.

It is a super-3 number, since 3×21986523765³ (a number of 32 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 27143452 + ... + 27144261.

Almost surely, 2^21986523765 is an apocalyptic number.

It is an amenable number.

21986523765 is a deficient number, since it is larger than the sum of its proper divisors (17426356599).

21986523765 is an equidigital number, since it uses as much as digits as its factorization.

21986523765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54287730 (or 54287721 counting only the distinct ones).

The product of its digits is 5443200, while the sum is 54.

The spelling of 21986523765 in words is "twenty-one billion, nine hundred eighty-six million, five hundred twenty-three thousand, seven hundred sixty-five".