81985121 has 2 divisors, whose sum is σ = 81985122. Its totient is φ = 81985120.

The previous prime is 81985103. The next prime is 81985147. The reversal of 81985121 is 12158918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69488896 + 12496225 = 8336^2 + 3535^2 .

It is a cyclic number.

It is not a de Polignac number, because 81985121 - 2¹⁴ = 81968737 is a prime.

It is not a weakly prime, because it can be changed into another prime (81985151) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40992560 + 40992561.

It is an arithmetic number, because the mean of its divisors is an integer number (40992561).

Almost surely, 2^81985121 is an apocalyptic number.

It is an amenable number.

81985121 is a deficient number, since it is larger than the sum of its proper divisors (1).

81985121 is an equidigital number, since it uses as much as digits as its factorization.

81985121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5760, while the sum is 35.

The square root of 81985121 is about 9054.5635455277. The cubic root of 81985121 is about 434.4218699386.

The spelling of 81985121 in words is "eighty-one million, nine hundred eighty-five thousand, one hundred twenty-one".