81209893 has 2 divisors, whose sum is σ = 81209894. Its totient is φ = 81209892.

The previous prime is 81209881. The next prime is 81209911. The reversal of 81209893 is 39890218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81036004 + 173889 = 9002^2 + 417^2 .

It is a cyclic number.

It is not a de Polignac number, because 81209893 - 2⁵ = 81209861 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81209873) 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 as a sum of consecutive naturals, namely, 40604946 + 40604947.

It is an arithmetic number, because the mean of its divisors is an integer number (40604947).

Almost surely, 2^81209893 is an apocalyptic number.

It is an amenable number.

81209893 is a deficient number, since it is larger than the sum of its proper divisors (1).

81209893 is an equidigital number, since it uses as much as digits as its factorization.

81209893 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 81209893 is about 9011.6531779691. The cubic root of 81209893 is about 433.0482747835.

The spelling of 81209893 in words is "eighty-one million, two hundred nine thousand, eight hundred ninety-three".