81389191853509 has 2 divisors, whose sum is σ = 81389191853510. Its totient is φ = 81389191853508.

The previous prime is 81389191853507. The next prime is 81389191853513. The reversal of 81389191853509 is 90535819198318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70474295640609 + 10914896212900 = 8394897^2 + 3303770^2 .

It is a cyclic number.

It is not a de Polignac number, because 81389191853509 - 2¹ = 81389191853507 is a prime.

It is a super-2 number, since 2×81389191853509² (a number of 29 digits) contains 22 as substring.

Together with 81389191853507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81389191853507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40694595926754 + 40694595926755.

It is an arithmetic number, because the mean of its divisors is an integer number (40694595926755).

Almost surely, 2^{81389191853509} is an apocalyptic number.

It is an amenable number.

81389191853509 is a deficient number, since it is larger than the sum of its proper divisors (1).

81389191853509 is an equidigital number, since it uses as much as digits as its factorization.

81389191853509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 83980800, while the sum is 70.

The spelling of 81389191853509 in words is "eighty-one trillion, three hundred eighty-nine billion, one hundred ninety-one million, eight hundred fifty-three thousand, five hundred nine".