81368781 has 16 divisors (see below), whose sum is σ = 117296256. Its totient is φ = 49876416.

The previous prime is 81368767. The next prime is 81368803. The reversal of 81368781 is 18786318.

It is not a de Polignac number, because 81368781 - 2⁷ = 81368653 is a prime.

It is a super-2 number, since 2×81368781² = 13241757042851922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81368711) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6291 + ... + 14223.

It is an arithmetic number, because the mean of its divisors is an integer number (7331016).

Almost surely, 2^81368781 is an apocalyptic number.

It is an amenable number.

81368781 is a deficient number, since it is larger than the sum of its proper divisors (35927475).

81368781 is a wasteful number, since it uses less digits than its factorization.

81368781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8212.

The product of its digits is 64512, while the sum is 42.

The square root of 81368781 is about 9020.4645667504. The cubic root of 81368781 is about 433.3305119474.

The spelling of 81368781 in words is "eighty-one million, three hundred sixty-eight thousand, seven hundred eighty-one".