81491483537 has 2 divisors, whose sum is σ = 81491483538. Its totient is φ = 81491483536.

The previous prime is 81491483503. The next prime is 81491483551. The reversal of 81491483537 is 73538419418.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 52305519616 + 29185963921 = 228704^2 + 170839^2 .

It is a cyclic number.

It is not a de Polignac number, because 81491483537 - 2⁶ = 81491483473 is a prime.

It is a super-2 number, since 2×81491483537² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81491483137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40745741768 + 40745741769.

It is an arithmetic number, because the mean of its divisors is an integer number (40745741769).

Almost surely, 2^81491483537 is an apocalyptic number.

It is an amenable number.

81491483537 is a deficient number, since it is larger than the sum of its proper divisors (1).

81491483537 is an equidigital number, since it uses as much as digits as its factorization.

81491483537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2903040, while the sum is 53.

The spelling of 81491483537 in words is "eighty-one billion, four hundred ninety-one million, four hundred eighty-three thousand, five hundred thirty-seven".