81707881 has 2 divisors, whose sum is σ = 81707882. Its totient is φ = 81707880.

The previous prime is 81707867. The next prime is 81707897. The reversal of 81707881 is 18870718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54834025 + 26873856 = 7405^2 + 5184^2 .

It is a cyclic number.

It is not a de Polignac number, because 81707881 - 2⁹ = 81707369 is a prime.

It is a super-2 number, since 2×81707881² = 13352355635020322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81807881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40853940 + 40853941.

It is an arithmetic number, because the mean of its divisors is an integer number (40853941).

Almost surely, 2^81707881 is an apocalyptic number.

It is an amenable number.

81707881 is a deficient number, since it is larger than the sum of its proper divisors (1).

81707881 is an equidigital number, since it uses as much as digits as its factorization.

81707881 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25088, while the sum is 40.

The square root of 81707881 is about 9039.2411739039. The cubic root of 81707881 is about 433.9316381668.

The spelling of 81707881 in words is "eighty-one million, seven hundred seven thousand, eight hundred eighty-one".