81811577 has 2 divisors, whose sum is σ = 81811578. Its totient is φ = 81811576.

The previous prime is 81811567. The next prime is 81811589. The reversal of 81811577 is 77511818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 53816896 + 27994681 = 7336^2 + 5291^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81811577 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81811577.

It is not a weakly prime, because it can be changed into another prime (81811517) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40905788 + 40905789.

It is an arithmetic number, because the mean of its divisors is an integer number (40905789).

Almost surely, 2^81811577 is an apocalyptic number.

It is an amenable number.

81811577 is a deficient number, since it is larger than the sum of its proper divisors (1).

81811577 is an equidigital number, since it uses as much as digits as its factorization.

81811577 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15680, while the sum is 38.

The square root of 81811577 is about 9044.9752349025. The cubic root of 81811577 is about 434.1151290479.

The spelling of 81811577 in words is "eighty-one million, eight hundred eleven thousand, five hundred seventy-seven".