81805620 has 48 divisors (see below), whose sum is σ = 246677760. Its totient is φ = 20136576.

The previous prime is 81805613. The next prime is 81805639. The reversal of 81805620 is 2650818.

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

It is a congruent number.

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, 51660 + ... + 53219.

It is an arithmetic number, because the mean of its divisors is an integer number (5139120).

Almost surely, 2^81805620 is an apocalyptic number.

It is an amenable number.

81805620 is an abundant number, since it is smaller than the sum of its proper divisors (164872140).

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

81805620 is a wasteful number, since it uses less digits than its factorization.

81805620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104904 (or 104902 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 30.

The square root of 81805620 is about 9044.6459300517. The cubic root of 81805620 is about 434.1045922890.

The spelling of 81805620 in words is "eighty-one million, eight hundred five thousand, six hundred twenty".