81389813537 has 2 divisors, whose sum is σ = 81389813538. Its totient is φ = 81389813536.

The previous prime is 81389813507. The next prime is 81389813563. The reversal of 81389813537 is 73531898318.

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., 81389813521 + 16 = 285289^2 + 4^2 .

It is a cyclic number.

It is not a de Polignac number, because 81389813537 - 2³⁶ = 12670336801 is a prime.

It is not a weakly prime, because it can be changed into another prime (81389813507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40694906768 + 40694906769.

It is an arithmetic number, because the mean of its divisors is an integer number (40694906769).

Almost surely, 2^81389813537 is an apocalyptic number.

It is an amenable number.

81389813537 is a deficient number, since it is larger than the sum of its proper divisors (1).

81389813537 is an equidigital number, since it uses as much as digits as its factorization.

81389813537 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4354560, while the sum is 56.

The spelling of 81389813537 in words is "eighty-one billion, three hundred eighty-nine million, eight hundred thirteen thousand, five hundred thirty-seven".