81866919 has 8 divisors (see below), whose sum is σ = 109237120. Its totient is φ = 54537336.

The previous prime is 81866909. The next prime is 81866921. The reversal of 81866919 is 91966818.

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

It is not a de Polignac number, because 81866919 - 2¹³ = 81858727 is a prime.

It is a super-2 number, since 2×81866919² = 13404384853105122, 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 (81866909) 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, 5089 + ... + 13770.

It is an arithmetic number, because the mean of its divisors is an integer number (13654640).

Almost surely, 2^81866919 is an apocalyptic number.

81866919 is a deficient number, since it is larger than the sum of its proper divisors (27370201).

81866919 is a wasteful number, since it uses less digits than its factorization.

81866919 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20309.

The product of its digits is 186624, while the sum is 48.

The square root of 81866919 is about 9048.0339853473. The cubic root of 81866919 is about 434.2129936988.

The spelling of 81866919 in words is "eighty-one million, eight hundred sixty-six thousand, nine hundred nineteen".