21756556815871 has 32 divisors (see below), whose sum is σ = 23062291200000. Its totient is φ = 20493537926400.

The previous prime is 21756556815827. The next prime is 21756556815887. The reversal of 21756556815871 is 17851865565712.

It is not a de Polignac number, because 21756556815871 - 2⁷ = 21756556815743 is a prime.

It is a Smith number, since the sum of its digits (67) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21756556815797 and 21756556815806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21756556815571) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 268396555 + ... + 268477603.

It is an arithmetic number, because the mean of its divisors is an integer number (720696600000).

Almost surely, 2^{21756556815871} is an apocalyptic number.

21756556815871 is a deficient number, since it is larger than the sum of its proper divisors (1305734384129).

21756556815871 is a wasteful number, since it uses less digits than its factorization.

21756556815871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82327.

The product of its digits is 141120000, while the sum is 67.

The spelling of 21756556815871 in words is "twenty-one trillion, seven hundred fifty-six billion, five hundred fifty-six million, eight hundred fifteen thousand, eight hundred seventy-one".