81665483640 has 256 divisors, whose sum is σ = 281749708800. Its totient is φ = 18782668800.

The previous prime is 81665483617. The next prime is 81665483659. The reversal of 81665483640 is 4638456618.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1373325 + ... + 1431555.

It is an arithmetic number, because the mean of its divisors is an integer number (1100584800).

Almost surely, 2^81665483640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81665483640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (140874854400).

81665483640 is an abundant number, since it is smaller than the sum of its proper divisors (200084225160).

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

81665483640 is a wasteful number, since it uses less digits than its factorization.

81665483640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58318 (or 58314 counting only the distinct ones).

The product of its (nonzero) digits is 3317760, while the sum is 51.

The spelling of 81665483640 in words is "eighty-one billion, six hundred sixty-five million, four hundred eighty-three thousand, six hundred forty".