81644915797 has 2 divisors, whose sum is σ = 81644915798. Its totient is φ = 81644915796.

The previous prime is 81644915771. The next prime is 81644915861. The reversal of 81644915797 is 79751944618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 43246945681 + 38397970116 = 207959^2 + 195954^2 .

It is a cyclic number.

It is not a de Polignac number, because 81644915797 - 2⁷ = 81644915669 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81644915747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40822457898 + 40822457899.

It is an arithmetic number, because the mean of its divisors is an integer number (40822457899).

Almost surely, 2^81644915797 is an apocalyptic number.

It is an amenable number.

81644915797 is a deficient number, since it is larger than the sum of its proper divisors (1).

81644915797 is an equidigital number, since it uses as much as digits as its factorization.

81644915797 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15240960, while the sum is 61.

It can be divided in two parts, 8164 and 4915797, that added together give a square (4923961 = 2219²).

The spelling of 81644915797 in words is "eighty-one billion, six hundred forty-four million, nine hundred fifteen thousand, seven hundred ninety-seven".