81369121 has 2 divisors, whose sum is σ = 81369122. Its totient is φ = 81369120.

The previous prime is 81369109. The next prime is 81369137. The reversal of 81369121 is 12196318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78074896 + 3294225 = 8836^2 + 1815^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81369121 is a prime.

It is not a weakly prime, because it can be changed into another prime (81369161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40684560 + 40684561.

It is an arithmetic number, because the mean of its divisors is an integer number (40684561).

Almost surely, 2^81369121 is an apocalyptic number.

It is an amenable number.

81369121 is a deficient number, since it is larger than the sum of its proper divisors (1).

81369121 is an equidigital number, since it uses as much as digits as its factorization.

81369121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2592, while the sum is 31.

The square root of 81369121 is about 9020.4834127667. The cubic root of 81369121 is about 433.3311155048.

The spelling of 81369121 in words is "eighty-one million, three hundred sixty-nine thousand, one hundred twenty-one".