81784160640 has 768 divisors, whose sum is σ = 357061461120. Its totient is φ = 16785211392.

The previous prime is 81784160611. The next prime is 81784160651. The reversal of 81784160640 is 4606148718.

81784160640 is a `hidden beast` number, since 8 + 178 + 416 + 0 + 64 + 0 = 666.

It is a hoax number, since the sum of its digits (45) 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 (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 19391812 + ... + 19396028.

Almost surely, 2^81784160640 is an apocalyptic number.

81784160640 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 81784160640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (178530730560).

81784160640 is an abundant number, since it is smaller than the sum of its proper divisors (275277300480).

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

81784160640 is a wasteful number, since it uses less digits than its factorization.

81784160640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4299 (or 4284 counting only the distinct ones).

The product of its (nonzero) digits is 258048, while the sum is 45.

The spelling of 81784160640 in words is "eighty-one billion, seven hundred eighty-four million, one hundred sixty thousand, six hundred forty".