81680761 has 2 divisors, whose sum is σ = 81680762. Its totient is φ = 81680760.

The previous prime is 81680759. The next prime is 81680771. The reversal of 81680761 is 16708618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55353600 + 26327161 = 7440^2 + 5131^2 .

It is a cyclic number.

It is not a de Polignac number, because 81680761 - 2¹ = 81680759 is a prime.

Together with 81680759, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 81680761.

It is not a weakly prime, because it can be changed into another prime (81680701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40840380 + 40840381.

It is an arithmetic number, because the mean of its divisors is an integer number (40840381).

Almost surely, 2^81680761 is an apocalyptic number.

It is an amenable number.

81680761 is a deficient number, since it is larger than the sum of its proper divisors (1).

81680761 is an equidigital number, since it uses as much as digits as its factorization.

81680761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 81680761 is about 9037.7409234830. The cubic root of 81680761 is about 433.8836235072.

The spelling of 81680761 in words is "eighty-one million, six hundred eighty thousand, seven hundred sixty-one".