81982820 has 12 divisors (see below), whose sum is σ = 172163964. Its totient is φ = 32793120.

The previous prime is 81982807. The next prime is 81982829. The reversal of 81982820 is 2828918.

It can be written as a sum of positive squares in 2 ways, for example, as 24344356 + 57638464 = 4934^2 + 7592^2 .

It is not an unprimeable number, because it can be changed into a prime (81982829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2049551 + ... + 2049590.

It is an arithmetic number, because the mean of its divisors is an integer number (14346997).

Almost surely, 2^81982820 is an apocalyptic number.

It is an amenable number.

81982820 is an abundant number, since it is smaller than the sum of its proper divisors (90181144).

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

81982820 is a wasteful number, since it uses less digits than its factorization.

81982820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4099150 (or 4099148 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 38.

The square root of 81982820 is about 9054.4364816371. The cubic root of 81982820 is about 434.4178057293.

The spelling of 81982820 in words is "eighty-one million, nine hundred eighty-two thousand, eight hundred twenty".