81399161 has 4 divisors (see below), whose sum is σ = 82514292. Its totient is φ = 80284032.

The previous prime is 81399127. The next prime is 81399187. The reversal of 81399161 is 16199318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16199318 = 2 ⋅8099659.

It can be written as a sum of positive squares in 2 ways, for example, as 41203561 + 40195600 = 6419^2 + 6340^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81399161 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81399191) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 557456 + ... + 557601.

It is an arithmetic number, because the mean of its divisors is an integer number (20628573).

Almost surely, 2^81399161 is an apocalyptic number.

It is an amenable number.

81399161 is a deficient number, since it is larger than the sum of its proper divisors (1115131).

81399161 is a wasteful number, since it uses less digits than its factorization.

81399161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1115130.

The product of its digits is 11664, while the sum is 38.

The square root of 81399161 is about 9022.1483583457. The cubic root of 81399161 is about 433.3844349334.

The spelling of 81399161 in words is "eighty-one million, three hundred ninety-nine thousand, one hundred sixty-one".