161371727521 has 3 divisors (see below), whose sum is σ = 161372129233. Its totient is φ = 161371325810.

The previous prime is 161371727501. The next prime is 161371727563. The reversal of 161371727521 is 125727173161.

The square root of 161371727521 is 401711.

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, and also an emirpimes, since its reverse is a distinct semiprime: 125727173161 = 8807 ⋅14275823.

It is not a de Polignac number, because 161371727521 - 2⁹ = 161371727009 is a prime.

It is a super-2 number, since 2×161371727521² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161371727501) 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, 200856 + ... + 602566.

Almost surely, 2^161371727521 is an apocalyptic number.

161371727521 is the 401711-st square number.

161371727521 is the 200856-th centered octagonal number.

It is an amenable number.

161371727521 is a deficient number, since it is larger than the sum of its proper divisors (401712).

161371727521 is an frugal number, since it uses more digits than its factorization.

161371727521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 803422 (or 401711 counting only the distinct ones).

The product of its digits is 123480, while the sum is 43.

The spelling of 161371727521 in words is "one hundred sixty-one billion, three hundred seventy-one million, seven hundred twenty-seven thousand, five hundred twenty-one".