81293985 has 12 divisors (see below), whose sum is σ = 140909652. Its totient is φ = 43356768.

The previous prime is 81293969. The next prime is 81293987. The reversal of 81293985 is 58939218.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 26873856 + 54420129 = 5184^2 + 7377^2 .

It is not a de Polignac number, because 81293985 - 2⁴ = 81293969 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45), and also a Moran number because the ratio is a prime number: 1806533 = 81293985 / (8 + 1 + 2 + 9 + 3 + 9 + 8 + 5).

It is a self number, because there is not a number n which added to its sum of digits gives 81293985.

It is not an unprimeable number, because it can be changed into a prime (81293987) 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, 903222 + ... + 903311.

It is an arithmetic number, because the mean of its divisors is an integer number (11742471).

Almost surely, 2^81293985 is an apocalyptic number.

It is an amenable number.

81293985 is a deficient number, since it is larger than the sum of its proper divisors (59615667).

81293985 is a wasteful number, since it uses less digits than its factorization.

81293985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1806544 (or 1806541 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 81293985 is about 9016.3177073570. The cubic root of 81293985 is about 433.1976955497.

The spelling of 81293985 in words is "eighty-one million, two hundred ninety-three thousand, nine hundred eighty-five".