85816781 has 2 divisors, whose sum is σ = 85816782. Its totient is φ = 85816780.

The previous prime is 85816769. The next prime is 85816837. The reversal of 85816781 is 18761858.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 67404100 + 18412681 = 8210^2 + 4291^2 .

It is a cyclic number.

It is not a de Polignac number, because 85816781 - 2²² = 81622477 is a prime.

It is a super-2 number, since 2×85816781² = 14729039802403922, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is equal to p_4988438 and since 85816781 and 4988438 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (85816741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42908390 + 42908391.

It is an arithmetic number, because the mean of its divisors is an integer number (42908391).

Almost surely, 2^85816781 is an apocalyptic number.

It is an amenable number.

85816781 is a deficient number, since it is larger than the sum of its proper divisors (1).

85816781 is an equidigital number, since it uses as much as digits as its factorization.

85816781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 107520, while the sum is 44.

The square root of 85816781 is about 9263.7347220222. The cubic root of 85816781 is about 441.0868123000.

The spelling of 85816781 in words is "eighty-five million, eight hundred sixteen thousand, seven hundred eighty-one".