81994193 has 2 divisors, whose sum is σ = 81994194. Its totient is φ = 81994192.

The previous prime is 81994189. The next prime is 81994229. The reversal of 81994193 is 39149918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 57866449 + 24127744 = 7607^2 + 4912^2 .

It is a cyclic number.

It is not a de Polignac number, because 81994193 - 2² = 81994189 is a prime.

It is not a weakly prime, because it can be changed into another prime (81996193) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40997096 + 40997097.

It is an arithmetic number, because the mean of its divisors is an integer number (40997097).

Almost surely, 2^81994193 is an apocalyptic number.

It is an amenable number.

81994193 is a deficient number, since it is larger than the sum of its proper divisors (1).

81994193 is an equidigital number, since it uses as much as digits as its factorization.

81994193 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 44.

The square root of 81994193 is about 9055.0644945246. The cubic root of 81994193 is about 434.4378928860.

The spelling of 81994193 in words is "eighty-one million, nine hundred ninety-four thousand, one hundred ninety-three".