86521781 has 4 divisors (see below), whose sum is σ = 86834412. Its totient is φ = 86209152.

The previous prime is 86521753. The next prime is 86521793. The reversal of 86521781 is 18712568.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 25150225 + 61371556 = 5015^2 + 7834^2 .

It is a cyclic number.

It is not a de Polignac number, because 86521781 - 2²⁶ = 19412917 is a prime.

It is a super-2 number, since 2×86521781² = 14972037174823922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (86521711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 155900 + ... + 156453.

It is an arithmetic number, because the mean of its divisors is an integer number (21708603).

Almost surely, 2^86521781 is an apocalyptic number.

It is an amenable number.

86521781 is a deficient number, since it is larger than the sum of its proper divisors (312631).

86521781 is a wasteful number, since it uses less digits than its factorization.

86521781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312630.

The product of its digits is 26880, while the sum is 38.

The square root of 86521781 is about 9301.7084989802. The cubic root of 86521781 is about 442.2913883628.

The spelling of 86521781 in words is "eighty-six million, five hundred twenty-one thousand, seven hundred eighty-one".