81451844137 has 4 divisors (see below), whose sum is σ = 81789818836. Its totient is φ = 81113869440.

The previous prime is 81451844093. The next prime is 81451844143. The reversal of 81451844137 is 73144815418.

It is a happy number.

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 37240894441 + 44210949696 = 192979^2 + 210264^2 .

It is a cyclic number.

It is not a de Polignac number, because 81451844137 - 2³¹ = 79304360489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81451841137) 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 3 ways as a sum of consecutive naturals, for example, 168986988 + ... + 168987469.

It is an arithmetic number, because the mean of its divisors is an integer number (20447454709).

Almost surely, 2^81451844137 is an apocalyptic number.

It is an amenable number.

81451844137 is a deficient number, since it is larger than the sum of its proper divisors (337974699).

81451844137 is a wasteful number, since it uses less digits than its factorization.

81451844137 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 337974698.

The product of its digits is 430080, while the sum is 46.

The spelling of 81451844137 in words is "eighty-one billion, four hundred fifty-one million, eight hundred forty-four thousand, one hundred thirty-seven".