661571721171 has 48 divisors (see below), whose sum is σ = 1003076186112. Its totient is φ = 419372712000.

The previous prime is 661571721103. The next prime is 661571721203. The reversal of 661571721171 is 171127175166.

661571721171 is a `hidden beast` number, since 6 + 6 + 1 + 571 + 7 + 2 + 1 + 1 + 71 = 666.

It is not a de Polignac number, because 661571721171 - 2⁹ = 661571720659 is a prime.

It is a super-2 number, since 2×661571721171² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661571728171) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 23998846 + ... + 24026396.

It is an arithmetic number, because the mean of its divisors is an integer number (20897420544).

Almost surely, 2^661571721171 is an apocalyptic number.

661571721171 is a deficient number, since it is larger than the sum of its proper divisors (341504464941).

661571721171 is a wasteful number, since it uses less digits than its factorization.

661571721171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28264 (or 28261 counting only the distinct ones).

The product of its digits is 123480, while the sum is 45.

The spelling of 661571721171 in words is "six hundred sixty-one billion, five hundred seventy-one million, seven hundred twenty-one thousand, one hundred seventy-one".