81707557 has 2 divisors, whose sum is σ = 81707558. Its totient is φ = 81707556.

The previous prime is 81707551. The next prime is 81707579. The reversal of 81707557 is 75570718.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 50893956 + 30813601 = 7134^2 + 5551^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81707557 is a prime.

It is a super-2 number, since 2×81707557² = 13352249741816498, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81707551) 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, 40853778 + 40853779.

It is an arithmetic number, because the mean of its divisors is an integer number (40853779).

Almost surely, 2^81707557 is an apocalyptic number.

It is an amenable number.

81707557 is a deficient number, since it is larger than the sum of its proper divisors (1).

81707557 is an equidigital number, since it uses as much as digits as its factorization.

81707557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 68600, while the sum is 40.

The square root of 81707557 is about 9039.2232520278. The cubic root of 81707557 is about 433.9310646030.

The spelling of 81707557 in words is "eighty-one million, seven hundred seven thousand, five hundred fifty-seven".