81878640 has 160 divisors (see below), whose sum is σ = 266607936. Its totient is φ = 20766720.

The previous prime is 81878639. The next prime is 81878659. The reversal of 81878640 is 4687818.

It is a super-2 number, since 2×81878640² = 13408223376499200, which contains 22 as substring.

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

It is a junction number, because it is equal to n+sod(n) for n = 81878592 and 81878601.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 521442 + ... + 521598.

Almost surely, 2^81878640 is an apocalyptic number.

81878640 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 81878640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (133303968).

81878640 is an abundant number, since it is smaller than the sum of its proper divisors (184729296).

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

81878640 is a wasteful number, since it uses less digits than its factorization.

81878640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267 (or 261 counting only the distinct ones).

The product of its (nonzero) digits is 86016, while the sum is 42.

The square root of 81878640 is about 9048.6816719343. The cubic root of 81878640 is about 434.2337150015.

The spelling of 81878640 in words is "eighty-one million, eight hundred seventy-eight thousand, six hundred forty".