81998806 has 4 divisors (see below), whose sum is σ = 122998212. Its totient is φ = 40999402.

The previous prime is 81998797. The next prime is 81998809. The reversal of 81998806 is 60889918.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81998806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81998809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20499700 + ... + 20499703.

It is an arithmetic number, because the mean of its divisors is an integer number (30749553).

Almost surely, 2^81998806 is an apocalyptic number.

81998806 is a deficient number, since it is larger than the sum of its proper divisors (40999406).

81998806 is a wasteful number, since it uses less digits than its factorization.

81998806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40999405.

The product of its (nonzero) digits is 248832, while the sum is 49.

The square root of 81998806 is about 9055.3192102764. The cubic root of 81998806 is about 434.4460399037.

The spelling of 81998806 in words is "eighty-one million, nine hundred ninety-eight thousand, eight hundred six".