81159779 has 2 divisors, whose sum is σ = 81159780. Its totient is φ = 81159778.

The previous prime is 81159769. The next prime is 81159839. The reversal of 81159779 is 97795118.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81159779 - 2⁴ = 81159763 is a prime.

It is not a weakly prime, because it can be changed into another prime (81159769) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40579889 + 40579890.

It is an arithmetic number, because the mean of its divisors is an integer number (40579890).

Almost surely, 2^81159779 is an apocalyptic number.

81159779 is a deficient number, since it is larger than the sum of its proper divisors (1).

81159779 is an equidigital number, since it uses as much as digits as its factorization.

81159779 is an evil number, because the sum of its binary digits is even.

The product of its digits is 158760, while the sum is 47.

The square root of 81159779 is about 9008.8722379663. The cubic root of 81159779 is about 432.9591795350.

The spelling of 81159779 in words is "eighty-one million, one hundred fifty-nine thousand, seven hundred seventy-nine".