81047531 has 2 divisors, whose sum is σ = 81047532. Its totient is φ = 81047530.

The previous prime is 81047513. The next prime is 81047537. The reversal of 81047531 is 13574018.

Together with previous prime (81047513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81047531 is a prime.

It is a super-2 number, since 2×81047531² = 13137404562391922, which contains 22 as substring.

It is equal to p_4727072 and since 81047531 and 4727072 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 81047494 and 81047503.

It is not a weakly prime, because it can be changed into another prime (81047537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40523765 + 40523766.

It is an arithmetic number, because the mean of its divisors is an integer number (40523766).

Almost surely, 2^81047531 is an apocalyptic number.

81047531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81047531 is an equidigital number, since it uses as much as digits as its factorization.

81047531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3360, while the sum is 29.

The square root of 81047531 is about 9002.6402238454. The cubic root of 81047531 is about 432.7594861045.

The spelling of 81047531 in words is "eighty-one million, forty-seven thousand, five hundred thirty-one".