81665502480 has 200 divisors, whose sum is σ = 284093328024. Its totient is φ = 21742387200.

The previous prime is 81665502473. The next prime is 81665502493. The reversal of 81665502480 is 8420556618.

81665502480 is a `hidden beast` number, since 8 + 1 + 6 + 65 + 502 + 4 + 80 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 24817591296 + 56847911184 = 157536^2 + 238428^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 4143850 + ... + 4163510.

Almost surely, 2^81665502480 is an apocalyptic number.

81665502480 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81665502480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (142046664012).

81665502480 is an abundant number, since it is smaller than the sum of its proper divisors (202427825544).

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

81665502480 is a wasteful number, since it uses less digits than its factorization.

81665502480 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20327 (or 20312 counting only the distinct ones).

The product of its (nonzero) digits is 460800, while the sum is 45.

The spelling of 81665502480 in words is "eighty-one billion, six hundred sixty-five million, five hundred two thousand, four hundred eighty".