81512197 has 4 divisors (see below), whose sum is σ = 87782380. Its totient is φ = 75242016.

The previous prime is 81512183. The next prime is 81512201. The reversal of 81512197 is 79121518.

It is a happy number.

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 29224836 + 52287361 = 5406^2 + 7231^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81512197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81512117) 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, 3135072 + ... + 3135097.

It is an arithmetic number, because the mean of its divisors is an integer number (21945595).

Almost surely, 2^81512197 is an apocalyptic number.

It is an amenable number.

81512197 is a deficient number, since it is larger than the sum of its proper divisors (6270183).

81512197 is a wasteful number, since it uses less digits than its factorization.

81512197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6270182.

The product of its digits is 5040, while the sum is 34.

The square root of 81512197 is about 9028.4105467131. The cubic root of 81512197 is about 433.5849504502.

The spelling of 81512197 in words is "eighty-one million, five hundred twelve thousand, one hundred ninety-seven".