81680487641 has 2 divisors, whose sum is σ = 81680487642. Its totient is φ = 81680487640.

The previous prime is 81680487619. The next prime is 81680487661. The reversal of 81680487641 is 14678408618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53981875600 + 27698612041 = 232340^2 + 166429^2 .

It is a cyclic number.

It is not a de Polignac number, because 81680487641 - 2²² = 81676293337 is a prime.

It is a super-2 number, since 2×81680487641² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81680487661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40840243820 + 40840243821.

It is an arithmetic number, because the mean of its divisors is an integer number (40840243821).

Almost surely, 2^81680487641 is an apocalyptic number.

It is an amenable number.

81680487641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81680487641 is an equidigital number, since it uses as much as digits as its factorization.

81680487641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2064384, while the sum is 53.

The spelling of 81680487641 in words is "eighty-one billion, six hundred eighty million, four hundred eighty-seven thousand, six hundred forty-one".