16171971630721 has 3 divisors (see below), whose sum is σ = 16171975652161. Its totient is φ = 16171967609282.

The previous prime is 16171971630679. The next prime is 16171971630811. The reversal of 16171971630721 is 12703617917161.

The square root of 16171971630721 is 4021439.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 16171971630721 - 2¹⁹ = 16171971106433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16171971636721) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2010720 + ... + 6032158.

Almost surely, 2^{16171971630721} is an apocalyptic number.

16171971630721 is the 4021439-th square number.

16171971630721 is the 2010720-th centered octagonal number.

It is an amenable number.

16171971630721 is a deficient number, since it is larger than the sum of its proper divisors (4021440).

16171971630721 is an frugal number, since it uses more digits than its factorization.

16171971630721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8042878 (or 4021439 counting only the distinct ones).

The product of its (nonzero) digits is 666792, while the sum is 52.

The spelling of 16171971630721 in words is "sixteen trillion, one hundred seventy-one billion, nine hundred seventy-one million, six hundred thirty thousand, seven hundred twenty-one".