81915947 has 2 divisors, whose sum is σ = 81915948. Its totient is φ = 81915946.

The previous prime is 81915941. The next prime is 81915959. The reversal of 81915947 is 74951918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81915947 - 2¹⁶ = 81850411 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81915898 and 81915907.

It is not a weakly prime, because it can be changed into another prime (81915941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40957973 + 40957974.

It is an arithmetic number, because the mean of its divisors is an integer number (40957974).

Almost surely, 2^81915947 is an apocalyptic number.

81915947 is a deficient number, since it is larger than the sum of its proper divisors (1).

81915947 is an equidigital number, since it uses as much as digits as its factorization.

81915947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 44.

The square root of 81915947 is about 9050.7428976853. The cubic root of 81915947 is about 434.2996560796.

The spelling of 81915947 in words is "eighty-one million, nine hundred fifteen thousand, nine hundred forty-seven".