81821449844 has 6 divisors (see below), whose sum is σ = 143187537234. Its totient is φ = 40910724920.

The previous prime is 81821449819. The next prime is 81821449847. The reversal of 81821449844 is 44894412818.

It can be written as a sum of positive squares in only one way, i.e., 73326140944 + 8495308900 = 270788^2 + 92170^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81821449847) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10227681227 + ... + 10227681234.

It is an arithmetic number, because the mean of its divisors is an integer number (23864589539).

Almost surely, 2^81821449844 is an apocalyptic number.

It is an amenable number.

81821449844 is a deficient number, since it is larger than the sum of its proper divisors (61366087390).

81821449844 is a wasteful number, since it uses less digits than its factorization.

81821449844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20455362465 (or 20455362463 counting only the distinct ones).

The product of its digits is 2359296, while the sum is 53.

The spelling of 81821449844 in words is "eighty-one billion, eight hundred twenty-one million, four hundred forty-nine thousand, eight hundred forty-four".