81406331536381 has 2 divisors, whose sum is σ = 81406331536382. Its totient is φ = 81406331536380.

The previous prime is 81406331536357. The next prime is 81406331536399. The reversal of 81406331536381 is 18363513360418.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 52525821400900 + 28880510135481 = 7247470^2 + 5374059^2 .

It is a cyclic number.

It is not a de Polignac number, because 81406331536381 - 2¹⁵ = 81406331503613 is a prime.

It is a super-2 number, since 2×81406331536381² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81406331536301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40703165768190 + 40703165768191.

It is an arithmetic number, because the mean of its divisors is an integer number (40703165768191).

Almost surely, 2^{81406331536381} is an apocalyptic number.

It is an amenable number.

81406331536381 is a deficient number, since it is larger than the sum of its proper divisors (1).

81406331536381 is an equidigital number, since it uses as much as digits as its factorization.

81406331536381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3732480, while the sum is 52.

Adding to 81406331536381 its reverse (18363513360418), we get a palindrome (99769844896799).

The spelling of 81406331536381 in words is "eighty-one trillion, four hundred six billion, three hundred thirty-one million, five hundred thirty-six thousand, three hundred eighty-one".