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81211711709 is a prime number
BaseRepresentation
bin100101110100010011…
…0000110000011011101
321202121210011101222102
41023220212012003131
52312310144233314
6101150320454445
75603334105542
oct1135046060335
9252553141872
1081211711709
1131494992017
12138a577a425
137873199cab
143d05a76bc9
1521a4a6e5de
hex12e89860dd

81211711709 has 2 divisors, whose sum is σ = 81211711710. Its totient is φ = 81211711708.

The previous prime is 81211711697. The next prime is 81211711733. The reversal of 81211711709 is 90711711218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 44458987609 + 36752724100 = 210853^2 + 191710^2 .

It is a cyclic number.

It is not a de Polignac number, because 81211711709 - 232 = 76916744413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81211711739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605855854 + 40605855855.

It is an arithmetic number, because the mean of its divisors is an integer number (40605855855).

Almost surely, 281211711709 is an apocalyptic number.

It is an amenable number.

81211711709 is a deficient number, since it is larger than the sum of its proper divisors (1).

81211711709 is an equidigital number, since it uses as much as digits as its factorization.

81211711709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7056, while the sum is 38.

The spelling of 81211711709 in words is "eighty-one billion, two hundred eleven million, seven hundred eleven thousand, seven hundred nine".