81605731 has 2 divisors, whose sum is σ = 81605732. Its totient is φ = 81605730.

The previous prime is 81605717. The next prime is 81605737. The reversal of 81605731 is 13750618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81605731 - 2⁷ = 81605603 is a prime.

It is a super-2 number, since 2×81605731² = 13318990664088722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81605693 and 81605702.

It is not a weakly prime, because it can be changed into another prime (81605737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40802865 + 40802866.

It is an arithmetic number, because the mean of its divisors is an integer number (40802866).

Almost surely, 2^81605731 is an apocalyptic number.

81605731 is a deficient number, since it is larger than the sum of its proper divisors (1).

81605731 is an equidigital number, since it uses as much as digits as its factorization.

81605731 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 31.

The square root of 81605731 is about 9033.5890431212. The cubic root of 81605731 is about 433.7507310903.

The spelling of 81605731 in words is "eighty-one million, six hundred five thousand, seven hundred thirty-one".