81670861440 has 896 divisors, whose sum is σ = 354471966720. Its totient is φ = 17557585920.

The previous prime is 81670861399. The next prime is 81670861477. The reversal of 81670861440 is 4416807618.

81670861440 is a `hidden beast` number, since 81 + 6 + 70 + 8 + 61 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (896).

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 111 ways as a sum of consecutive naturals, for example, 55519905 + ... + 55521375.

Almost surely, 2^81670861440 is an apocalyptic number.

81670861440 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 81670861440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (177235983360).

81670861440 is an abundant number, since it is smaller than the sum of its proper divisors (272801105280).

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

81670861440 is a wasteful number, since it uses less digits than its factorization.

81670861440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1532 (or 1505 counting only the distinct ones).

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

The spelling of 81670861440 in words is "eighty-one billion, six hundred seventy million, eight hundred sixty-one thousand, four hundred forty".