81185475840 has 576 divisors, whose sum is σ = 306093742080. Its totient is φ = 17955717120.

The previous prime is 81185475823. The next prime is 81185475857. The reversal of 81185475840 is 4857458118.

It is an interprime number because it is at equal distance from previous prime (81185475823) and next prime (81185475857).

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, 109858191 + ... + 109858929.

Almost surely, 2^81185475840 is an apocalyptic number.

81185475840 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 81185475840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (153046871040).

81185475840 is an abundant number, since it is smaller than the sum of its proper divisors (224908266240).

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

81185475840 is a wasteful number, since it uses less digits than its factorization.

81185475840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 898 (or 884 counting only the distinct ones).

The product of its (nonzero) digits is 1433600, while the sum is 51.

The spelling of 81185475840 in words is "eighty-one billion, one hundred eighty-five million, four hundred seventy-five thousand, eight hundred forty".