81521175312 has 30 divisors (see below), whose sum is σ = 228146067422. Its totient is φ = 27173725056.

The previous prime is 81521175311. The next prime is 81521175313. The reversal of 81521175312 is 21357112518.

81521175312 is a `hidden beast` number, since 8 + 1 + 5 + 2 + 117 + 531 + 2 = 666.

It is an interprime number because it is at equal distance from previous prime (81521175311) and next prime (81521175313).

It can be written as a sum of positive squares in only one way, i.e., 68667057936 + 12854117376 = 262044^2 + 113376^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81521175311) 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 5 ways as a sum of consecutive naturals, for example, 283059493 + ... + 283059780.

Almost surely, 2^81521175312 is an apocalyptic number.

It is an amenable number.

81521175312 is an abundant number, since it is smaller than the sum of its proper divisors (146624892110).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81521175312 is a wasteful number, since it uses less digits than its factorization.

81521175312 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 566119287 (or 566119278 counting only the distinct ones).

The product of its digits is 16800, while the sum is 36.

The spelling of 81521175312 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, three hundred twelve".