81492549961 has 3 divisors (see below), whose sum is σ = 81492835431. Its totient is φ = 81492264492.

The previous prime is 81492549917. The next prime is 81492549989. The reversal of 81492549961 is 16994529418.

The square root of 81492549961 is 285469.

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: 16994529418 = 2 ⋅8497264709.

It can be written as a sum of positive squares in only one way, i.e., 37920162361 + 43572387600 = 194731^2 + 208740^2 .

It is not a de Polignac number, because 81492549961 - 2¹⁵ = 81492517193 is a prime.

It is a super-2 number, since 2×81492549961² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81492549896 and 81492549905.

It is not an unprimeable number, because it can be changed into a prime (81492541961) 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, 142735 + ... + 428203.

It is an arithmetic number, because the mean of its divisors is an integer number (27164278477).

Almost surely, 2^81492549961 is an apocalyptic number.

81492549961 is the 285469-th square number.

81492549961 is the 142735-th centered octagonal number.

It is an amenable number.

81492549961 is a deficient number, since it is larger than the sum of its proper divisors (285470).

81492549961 is an frugal number, since it uses more digits than its factorization.

81492549961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 570938 (or 285469 counting only the distinct ones).

The product of its digits is 5598720, while the sum is 58.

The spelling of 81492549961 in words is "eighty-one billion, four hundred ninety-two million, five hundred forty-nine thousand, nine hundred sixty-one".