81810544381 has 8 divisors (see below), whose sum is σ = 83383167744. Its totient is φ = 80238996240.

The previous prime is 81810544379. The next prime is 81810544411. The reversal of 81810544381 is 18344501818.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81810544381 - 2¹ = 81810544379 is a prime.

It is a super-2 number, since 2×81810544381² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81810544331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 114325 + ... + 420346.

It is an arithmetic number, because the mean of its divisors is an integer number (10422895968).

Almost surely, 2^81810544381 is an apocalyptic number.

It is an amenable number.

81810544381 is a deficient number, since it is larger than the sum of its proper divisors (1572623363).

81810544381 is a wasteful number, since it uses less digits than its factorization.

81810544381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 537611.

The product of its (nonzero) digits is 122880, while the sum is 43.

The spelling of 81810544381 in words is "eighty-one billion, eight hundred ten million, five hundred forty-four thousand, three hundred eighty-one".