81159840 has 96 divisors (see below), whose sum is σ = 284074560. Its totient is φ = 21641472.

The previous prime is 81159839. The next prime is 81159899. The reversal of 81159840 is 4895118.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81159795 and 81159804.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5074 + ... + 13713.

It is an arithmetic number, because the mean of its divisors is an integer number (2959110).

Almost surely, 2^81159840 is an apocalyptic number.

81159840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81159840 is an abundant number, since it is smaller than the sum of its proper divisors (202914720).

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

81159840 is a wasteful number, since it uses less digits than its factorization.

81159840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18811 (or 18797 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 81159840 is about 9008.8756235171. The cubic root of 81159840 is about 432.9592880063.

It can be divided in two parts, 8115 and 9840, that added together give a triangular number (17955 = T₁₈₉).

The spelling of 81159840 in words is "eighty-one million, one hundred fifty-nine thousand, eight hundred forty".