81994666 has 8 divisors (see below), whose sum is σ = 132452964. Its totient is φ = 37843680.

The previous prime is 81994643. The next prime is 81994669. The reversal of 81994666 is 66649918.

It can be written as a sum of positive squares in 2 ways, for example, as 81378441 + 616225 = 9021^2 + 785^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (81994669) 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 3 ways as a sum of consecutive naturals, for example, 1576795 + ... + 1576846.

Almost surely, 2^81994666 is an apocalyptic number.

81994666 is a deficient number, since it is larger than the sum of its proper divisors (50458298).

81994666 is a wasteful number, since it uses less digits than its factorization.

81994666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3153656.

The product of its digits is 559872, while the sum is 49.

The square root of 81994666 is about 9055.0906124677. The cubic root of 81994666 is about 434.4387282652.

The spelling of 81994666 in words is "eighty-one million, nine hundred ninety-four thousand, six hundred sixty-six".