81791040 has 56 divisors (see below), whose sum is σ = 259689600. Its totient is φ = 21810688.

The previous prime is 81791033. The next prime is 81791071. The reversal of 81791040 is 4019718.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81790989 and 81791007.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41640 + ... + 43559.

Almost surely, 2^81791040 is an apocalyptic number.

81791040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81791040 is an abundant number, since it is smaller than the sum of its proper divisors (177898560).

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

81791040 is a wasteful number, since it uses less digits than its factorization.

81791040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85219 (or 85209 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 81791040 is about 9043.8398924351. The cubic root of 81791040 is about 434.0788009843.

The spelling of 81791040 in words is "eighty-one million, seven hundred ninety-one thousand, forty".