81802640 has 40 divisors (see below), whose sum is σ = 201382200. Its totient is φ = 30795776.

The previous prime is 81802603. The next prime is 81802663. The reversal of 81802640 is 4620818.

It can be written as a sum of positive squares in 4 ways, for example, as 10163344 + 71639296 = 3188^2 + 8464^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

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, 28715 + ... + 31434.

It is an arithmetic number, because the mean of its divisors is an integer number (5034555).

Almost surely, 2^81802640 is an apocalyptic number.

81802640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81802640 is an abundant number, since it is smaller than the sum of its proper divisors (119579560).

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

81802640 is a wasteful number, since it uses less digits than its factorization.

81802640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60179 (or 60173 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 29.

The square root of 81802640 is about 9044.4811902065. The cubic root of 81802640 is about 434.0993210644.

The spelling of 81802640 in words is "eighty-one million, eight hundred two thousand, six hundred forty".