85821781 has 2 divisors, whose sum is σ = 85821782. Its totient is φ = 85821780.

The previous prime is 85821779. The next prime is 85821829. The reversal of 85821781 is 18712858.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 85266756 + 555025 = 9234^2 + 745^2 .

It is a cyclic number.

It is not a de Polignac number, because 85821781 - 2¹ = 85821779 is a prime.

It is a super-2 number, since 2×85821781² = 14730756188023922, which contains 22 as substring.

Together with 85821779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85821761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42910890 + 42910891.

It is an arithmetic number, because the mean of its divisors is an integer number (42910891).

Almost surely, 2^85821781 is an apocalyptic number.

It is an amenable number.

85821781 is a deficient number, since it is larger than the sum of its proper divisors (1).

85821781 is an equidigital number, since it uses as much as digits as its factorization.

85821781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 35840, while the sum is 40.

The square root of 85821781 is about 9264.0045876500. The cubic root of 85821781 is about 441.0953785780.

The spelling of 85821781 in words is "eighty-five million, eight hundred twenty-one thousand, seven hundred eighty-one".