81389873 has 2 divisors, whose sum is σ = 81389874. Its totient is φ = 81389872.

The previous prime is 81389857. The next prime is 81389953. The reversal of 81389873 is 37898318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 58186384 + 23203489 = 7628^2 + 4817^2 .

It is a cyclic number.

It is not a de Polignac number, because 81389873 - 2⁴ = 81389857 is a prime.

It is a super-2 number, since 2×81389873² = 13248622853912258, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81379873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40694936 + 40694937.

It is an arithmetic number, because the mean of its divisors is an integer number (40694937).

Almost surely, 2^81389873 is an apocalyptic number.

It is an amenable number.

81389873 is a deficient number, since it is larger than the sum of its proper divisors (1).

81389873 is an equidigital number, since it uses as much as digits as its factorization.

81389873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 47.

The square root of 81389873 is about 9021.6336103834. The cubic root of 81389873 is about 433.3679506204.

The spelling of 81389873 in words is "eighty-one million, three hundred eighty-nine thousand, eight hundred seventy-three".