81723707520 has 768 divisors, whose sum is σ = 334295942400. Its totient is φ = 16517136384.

The previous prime is 81723707473. The next prime is 81723707567. The reversal of 81723707520 is 2570732718.

It is an interprime number because it is at equal distance from previous prime (81723707473) and next prime (81723707567).

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 643493697 + ... + 643493823.

It is an arithmetic number, because the mean of its divisors is an integer number (435281175).

Almost surely, 2^81723707520 is an apocalyptic number.

81723707520 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 81723707520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (167147971200).

81723707520 is an abundant number, since it is smaller than the sum of its proper divisors (252572234880).

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

81723707520 is a wasteful number, since it uses less digits than its factorization.

81723707520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325 (or 186 counting only the distinct ones).

The product of its (nonzero) digits is 164640, while the sum is 42.

The spelling of 81723707520 in words is "eighty-one billion, seven hundred twenty-three million, seven hundred seven thousand, five hundred twenty".