81288857 has 4 divisors (see below), whose sum is σ = 87541860. Its totient is φ = 75035856.

The previous prime is 81288853. The next prime is 81288871. The reversal of 81288857 is 75888218.

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 34762816 + 46526041 = 5896^2 + 6821^2 .

It is a cyclic number.

It is not a de Polignac number, because 81288857 - 2² = 81288853 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81288853) 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, 3126482 + ... + 3126507.

It is an arithmetic number, because the mean of its divisors is an integer number (21885465).

Almost surely, 2^81288857 is an apocalyptic number.

It is an amenable number.

81288857 is a deficient number, since it is larger than the sum of its proper divisors (6253003).

81288857 is a wasteful number, since it uses less digits than its factorization.

81288857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6253002.

The product of its digits is 286720, while the sum is 47.

The square root of 81288857 is about 9016.0333295746. The cubic root of 81288857 is about 433.1885866983.

The spelling of 81288857 in words is "eighty-one million, two hundred eighty-eight thousand, eight hundred fifty-seven".