81361897 has 4 divisors (see below), whose sum is σ = 81908100. Its totient is φ = 80815696.

The previous prime is 81361883. The next prime is 81361909. The reversal of 81361897 is 79816318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2702736 + 78659161 = 1644^2 + 8869^2 .

It is a cyclic number.

It is not a de Polignac number, because 81361897 - 2²³ = 72973289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81361807) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 272878 + ... + 273175.

It is an arithmetic number, because the mean of its divisors is an integer number (20477025).

Almost surely, 2^81361897 is an apocalyptic number.

It is an amenable number.

81361897 is a deficient number, since it is larger than the sum of its proper divisors (546203).

81361897 is a wasteful number, since it uses less digits than its factorization.

81361897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546202.

The product of its digits is 72576, while the sum is 43.

The square root of 81361897 is about 9020.0829818799. The cubic root of 81361897 is about 433.3182913253.

The spelling of 81361897 in words is "eighty-one million, three hundred sixty-one thousand, eight hundred ninety-seven".