81531897 has 4 divisors (see below), whose sum is σ = 108709200. Its totient is φ = 54354596.

The previous prime is 81531893. The next prime is 81531899. The reversal of 81531897 is 79813518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81531897 - 2² = 81531893 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81531893) 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, 13588647 + ... + 13588652.

It is an arithmetic number, because the mean of its divisors is an integer number (27177300).

Almost surely, 2^81531897 is an apocalyptic number.

It is an amenable number.

81531897 is a deficient number, since it is larger than the sum of its proper divisors (27177303).

81531897 is a wasteful number, since it uses less digits than its factorization.

81531897 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27177302.

The product of its digits is 60480, while the sum is 42.

The square root of 81531897 is about 9029.5014812558. The cubic root of 81531897 is about 433.6198774747.

It can be divided in two parts, 81531 and 897, that added together give a palindrome (82428).

The spelling of 81531897 in words is "eighty-one million, five hundred thirty-one thousand, eight hundred ninety-seven".