21756616161 has 32 divisors (see below), whose sum is σ = 34266028800. Its totient is φ = 12019228416.

The previous prime is 21756616157. The next prime is 21756616163. The reversal of 21756616161 is 16161665712.

It is a happy number.

It is not a de Polignac number, because 21756616161 - 2² = 21756616157 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21756616163) 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 31 ways as a sum of consecutive naturals, for example, 32815 + ... + 211163.

It is an arithmetic number, because the mean of its divisors is an integer number (1070813400).

Almost surely, 2^21756616161 is an apocalyptic number.

21756616161 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21756616161 is a deficient number, since it is larger than the sum of its proper divisors (12509412639).

21756616161 is a wasteful number, since it uses less digits than its factorization.

21756616161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178553.

The product of its digits is 90720, while the sum is 42.

The spelling of 21756616161 in words is "twenty-one billion, seven hundred fifty-six million, six hundred sixteen thousand, one hundred sixty-one".