81851768 has 8 divisors (see below), whose sum is σ = 153472080. Its totient is φ = 40925880.

The previous prime is 81851743. The next prime is 81851789. The reversal of 81851768 is 86715818.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5115728 + ... + 5115743.

It is an arithmetic number, because the mean of its divisors is an integer number (19184010).

Almost surely, 2^81851768 is an apocalyptic number.

It is an amenable number.

81851768 is a deficient number, since it is larger than the sum of its proper divisors (71620312).

81851768 is a wasteful number, since it uses less digits than its factorization.

81851768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10231477 (or 10231473 counting only the distinct ones).

The product of its digits is 107520, while the sum is 44.

The square root of 81851768 is about 9047.1966928989. The cubic root of 81851768 is about 434.1862056423.

The spelling of 81851768 in words is "eighty-one million, eight hundred fifty-one thousand, seven hundred sixty-eight".