81491136469 has 2 divisors, whose sum is σ = 81491136470. Its totient is φ = 81491136468.

The previous prime is 81491136367. The next prime is 81491136479. The reversal of 81491136469 is 96463119418.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60867304369 + 20623832100 = 246713^2 + 143610^2 .

It is a cyclic number.

It is not a de Polignac number, because 81491136469 - 2⁷ = 81491136341 is a prime.

It is a super-2 number, since 2×81491136469² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81491136479) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40745568234 + 40745568235.

It is an arithmetic number, because the mean of its divisors is an integer number (40745568235).

Almost surely, 2^81491136469 is an apocalyptic number.

It is an amenable number.

81491136469 is a deficient number, since it is larger than the sum of its proper divisors (1).

81491136469 is an equidigital number, since it uses as much as digits as its factorization.

81491136469 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1119744, while the sum is 52.

The spelling of 81491136469 in words is "eighty-one billion, four hundred ninety-one million, one hundred thirty-six thousand, four hundred sixty-nine".