81851815 has 8 divisors (see below), whose sum is σ = 98873568. Its totient is φ = 65047200.

The previous prime is 81851789. The next prime is 81851827. The reversal of 81851815 is 51815818.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81851815 - 2⁹ = 81851303 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53452 + ... + 54961.

It is an arithmetic number, because the mean of its divisors is an integer number (12359196).

Almost surely, 2^81851815 is an apocalyptic number.

81851815 is a deficient number, since it is larger than the sum of its proper divisors (17021753).

81851815 is a wasteful number, since it uses less digits than its factorization.

81851815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108569.

The product of its digits is 12800, while the sum is 37.

The square root of 81851815 is about 9047.1992903882. The cubic root of 81851815 is about 434.1862887468.

It can be divided in two parts, 8185 and 1815, that added together give a 4-th power (10000 = 10⁴).

The spelling of 81851815 in words is "eighty-one million, eight hundred fifty-one thousand, eight hundred fifteen".