81681192 has 48 divisors (see below), whose sum is σ = 234236340. Its totient is φ = 25625088.

The previous prime is 81681191. The next prime is 81681239. The reversal of 81681192 is 29118618.

It can be written as a sum of positive squares in 2 ways, for example, as 63584676 + 18096516 = 7974^2 + 4254^2 .

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 (81681191) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 32143 + ... + 34590.

Almost surely, 2^81681192 is an apocalyptic number.

It is an amenable number.

81681192 is an abundant number, since it is smaller than the sum of its proper divisors (152555148).

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

81681192 is a wasteful number, since it uses less digits than its factorization.

81681192 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66762 (or 66755 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 81681192 is about 9037.7647679058. The cubic root of 81681192 is about 433.8843866551.

The spelling of 81681192 in words is "eighty-one million, six hundred eighty-one thousand, one hundred ninety-two".