81861819 has 8 divisors (see below), whose sum is σ = 117545232. Its totient is φ = 50376480.

The previous prime is 81861803. The next prime is 81861869. The reversal of 81861819 is 91816818.

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

It is not a de Polignac number, because 81861819 - 2⁴ = 81861803 is a prime.

It is a super-2 number, since 2×81861819² = 13402714819977522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81861869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1049472 + ... + 1049549.

It is an arithmetic number, because the mean of its divisors is an integer number (14693154).

Almost surely, 2^81861819 is an apocalyptic number.

81861819 is a deficient number, since it is larger than the sum of its proper divisors (35683413).

81861819 is a wasteful number, since it uses less digits than its factorization.

81861819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2099037.

The product of its digits is 27648, while the sum is 42.

The square root of 81861819 is about 9047.7521517778. The cubic root of 81861819 is about 434.2039769015.

The spelling of 81861819 in words is "eighty-one million, eight hundred sixty-one thousand, eight hundred nineteen".