85686321781 has 2 divisors, whose sum is σ = 85686321782. Its totient is φ = 85686321780.

The previous prime is 85686321761. The next prime is 85686321821. The reversal of 85686321781 is 18712368658.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76236732100 + 9449589681 = 276110^2 + 97209^2 .

It is a cyclic number.

It is not a de Polignac number, because 85686321781 - 2³¹ = 83538838133 is a prime.

It is a super-2 number, since 2×85686321781² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85686321761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42843160890 + 42843160891.

It is an arithmetic number, because the mean of its divisors is an integer number (42843160891).

Almost surely, 2^85686321781 is an apocalyptic number.

It is an amenable number.

85686321781 is a deficient number, since it is larger than the sum of its proper divisors (1).

85686321781 is an equidigital number, since it uses as much as digits as its factorization.

85686321781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3870720, while the sum is 55.

The spelling of 85686321781 in words is "eighty-five billion, six hundred eighty-six million, three hundred twenty-one thousand, seven hundred eighty-one".