81287449 has 4 divisors (see below), whose sum is σ = 81338164. Its totient is φ = 81236736.

The previous prime is 81287447. The next prime is 81287467. The reversal of 81287449 is 94478218.

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 46854025 + 34433424 = 6845^2 + 5868^2 .

It is a cyclic number.

It is not a de Polignac number, because 81287449 - 2¹ = 81287447 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81287447) 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, 22872 + ... + 26185.

It is an arithmetic number, because the mean of its divisors is an integer number (20334541).

Almost surely, 2^81287449 is an apocalyptic number.

It is an amenable number.

81287449 is a deficient number, since it is larger than the sum of its proper divisors (50715).

81287449 is a wasteful number, since it uses less digits than its factorization.

81287449 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50714.

The product of its digits is 129024, while the sum is 43.

The square root of 81287449 is about 9015.9552461179. The cubic root of 81287449 is about 433.1860856050.

The spelling of 81287449 in words is "eighty-one million, two hundred eighty-seven thousand, four hundred forty-nine".