16651579681 has 9 divisors (see below), whose sum is σ = 18304536369. Its totient is φ = 15136509300.

The previous prime is 16651579673. The next prime is 16651579691. The reversal of 16651579681 is 18697515661.

The square root of 16651579681 is 129041.

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

It is not a de Polignac number, because 16651579681 - 2³ = 16651579673 is a prime.

It is a super-2 number, since 2×16651579681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16651579691) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 1413586 + ... + 1425316.

Almost surely, 2^16651579681 is an apocalyptic number.

16651579681 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

16651579681 is the 129041-st square number.

16651579681 is the 64521-st centered octagonal number.

It is an amenable number.

16651579681 is a deficient number, since it is larger than the sum of its proper divisors (1652956688).

16651579681 is an frugal number, since it uses more digits than its factorization.

16651579681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23484 (or 11742 counting only the distinct ones).

The product of its digits is 2721600, while the sum is 55.

The spelling of 16651579681 in words is "sixteen billion, six hundred fifty-one million, five hundred seventy-nine thousand, six hundred eighty-one".