81998740 has 24 divisors (see below), whose sum is σ = 172419912. Its totient is φ = 32757120.

The previous prime is 81998671. The next prime is 81998743. The reversal of 81998740 is 4789918.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 38912644 + 43086096 = 6238^2 + 6564^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81998743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16642 + ... + 20998.

It is an arithmetic number, because the mean of its divisors is an integer number (7184163).

Almost surely, 2^81998740 is an apocalyptic number.

It is an amenable number.

81998740 is an abundant number, since it is smaller than the sum of its proper divisors (90421172).

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

81998740 is a wasteful number, since it uses less digits than its factorization.

81998740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5307 (or 5305 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 46.

The square root of 81998740 is about 9055.3155660087. The cubic root of 81998740 is about 434.4459233432.

The spelling of 81998740 in words is "eighty-one million, nine hundred ninety-eight thousand, seven hundred forty".