815840640 has 256 divisors, whose sum is σ = 2984601600. Its totient is φ = 210401280.

The previous prime is 815840629. The next prime is 815840681. The reversal of 815840640 is 46048518.

815840640 is a `hidden beast` number, since 8 + 1 + 5 + 8 + 4 + 0 + 640 = 666.

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 = 815840595 and 815840604.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 534919 + ... + 536441.

It is an arithmetic number, because the mean of its divisors is an integer number (11658600).

Almost surely, 2^815840640 is an apocalyptic number.

815840640 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 815840640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1492300800).

815840640 is an abundant number, since it is smaller than the sum of its proper divisors (2168760960).

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

815840640 is a wasteful number, since it uses less digits than its factorization.

815840640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1582 (or 1564 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 36.

The square root of 815840640 is about 28562.9242200444. The cubic root of 815840640 is about 934.4049098228.

The spelling of 815840640 in words is "eight hundred fifteen million, eight hundred forty thousand, six hundred forty".