81393889 has 2 divisors, whose sum is σ = 81393890. Its totient is φ = 81393888.

The previous prime is 81393869. The next prime is 81393911. The reversal of 81393889 is 98839318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81360400 + 33489 = 9020^2 + 183^2 .

It is a cyclic number.

It is not a de Polignac number, because 81393889 - 2¹¹ = 81391841 is a prime.

It is not a weakly prime, because it can be changed into another prime (81393869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40696944 + 40696945.

It is an arithmetic number, because the mean of its divisors is an integer number (40696945).

Almost surely, 2^81393889 is an apocalyptic number.

It is an amenable number.

81393889 is a deficient number, since it is larger than the sum of its proper divisors (1).

81393889 is an equidigital number, since it uses as much as digits as its factorization.

81393889 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 373248, while the sum is 49.

The square root of 81393889 is about 9021.8561837351. The cubic root of 81393889 is about 433.3750783584.

The spelling of 81393889 in words is "eighty-one million, three hundred ninety-three thousand, eight hundred eighty-nine".