81998144 has 14 divisors (see below), whose sum is σ = 162715194. Its totient is φ = 40999040.

The previous prime is 81998143. The next prime is 81998177. The reversal of 81998144 is 44189918.

It can be written as a sum of positive squares in only one way, i.e., 65286400 + 16711744 = 8080^2 + 4088^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81998095 and 81998104.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81998143) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 640547 + ... + 640674.

Almost surely, 2^81998144 is an apocalyptic number.

It is an amenable number.

81998144 is a deficient number, since it is larger than the sum of its proper divisors (80717050).

81998144 is a wasteful number, since it uses less digits than its factorization.

81998144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1281233 (or 1281223 counting only the distinct ones).

The product of its digits is 82944, while the sum is 44.

The square root of 81998144 is about 9055.2826571013. The cubic root of 81998144 is about 434.4448707645. Note that the first 3 decimals are identical.

The spelling of 81998144 in words is "eighty-one million, nine hundred ninety-eight thousand, one hundred forty-four".