21661011171 has 20 divisors (see below), whose sum is σ = 32370525000. Its totient is φ = 14434998336.

The previous prime is 21661011133. The next prime is 21661011217. The reversal of 21661011171 is 17111016612.

21661011171 is a `hidden beast` number, since 21 + 6 + 610 + 11 + 17 + 1 = 666.

It is not a de Polignac number, because 21661011171 - 2³⁰ = 20587269347 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21661011131) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 160080 + ... + 262578.

It is an arithmetic number, because the mean of its divisors is an integer number (1618526250).

Almost surely, 2^21661011171 is an apocalyptic number.

21661011171 is a deficient number, since it is larger than the sum of its proper divisors (10709513829).

21661011171 is a wasteful number, since it uses less digits than its factorization.

21661011171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105120 (or 105111 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 27.

Adding to 21661011171 its reverse (17111016612), we get a palindrome (38772027783).

The spelling of 21661011171 in words is "twenty-one billion, six hundred sixty-one million, eleven thousand, one hundred seventy-one".