85811781 has 32 divisors (see below), whose sum is σ = 131217408. Its totient is φ = 49375040.

The previous prime is 85811777. The next prime is 85811849. The reversal of 85811781 is 18711858.

It is not a de Polignac number, because 85811781 - 2² = 85811777 is a prime.

It is a super-2 number, since 2×85811781² = 14727323516783922, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (85811701) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 126415 + ... + 127091.

It is an arithmetic number, because the mean of its divisors is an integer number (4100544).

Almost surely, 2^85811781 is an apocalyptic number.

It is an amenable number.

85811781 is a deficient number, since it is larger than the sum of its proper divisors (45405627).

85811781 is a wasteful number, since it uses less digits than its factorization.

85811781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 881.

The product of its digits is 17920, while the sum is 39.

The square root of 85811781 is about 9263.4648485326. The cubic root of 85811781 is about 441.0782456891.

The spelling of 85811781 in words is "eighty-five million, eight hundred eleven thousand, seven hundred eighty-one".