81399312 has 30 divisors (see below), whose sum is σ = 227805422. Its totient is φ = 27133056.

The previous prime is 81399293. The next prime is 81399313. The reversal of 81399312 is 21399318.

It can be written as a sum of positive squares in only one way, i.e., 72182016 + 9217296 = 8496^2 + 3036^2 .

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

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (81399313) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 282493 + ... + 282780.

Almost surely, 2^81399312 is an apocalyptic number.

It is an amenable number.

81399312 is an abundant number, since it is smaller than the sum of its proper divisors (146406110).

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

81399312 is a wasteful number, since it uses less digits than its factorization.

81399312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 565287 (or 565278 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 81399312 is about 9022.1567266369. The cubic root of 81399312 is about 433.3847029174.

The spelling of 81399312 in words is "eighty-one million, three hundred ninety-nine thousand, three hundred twelve".