21545723727 has 12 divisors (see below), whose sum is σ = 33950837544. Its totient is φ = 13058014320.

The previous prime is 21545723723. The next prime is 21545723729. The reversal of 21545723727 is 72732754512.

21545723727 is a `hidden beast` number, since 2 + 1 + 5 + 4 + 572 + 3 + 72 + 7 = 666.

It is not a de Polignac number, because 21545723727 - 2² = 21545723723 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545723723) 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 11 ways as a sum of consecutive naturals, for example, 108816688 + ... + 108816885.

It is an arithmetic number, because the mean of its divisors is an integer number (2829236462).

Almost surely, 2^21545723727 is an apocalyptic number.

21545723727 is a deficient number, since it is larger than the sum of its proper divisors (12405113817).

21545723727 is a wasteful number, since it uses less digits than its factorization.

21545723727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217633590 (or 217633587 counting only the distinct ones).

The product of its digits is 823200, while the sum is 45.

The spelling of 21545723727 in words is "twenty-one billion, five hundred forty-five million, seven hundred twenty-three thousand, seven hundred twenty-seven".