81092781 has 24 divisors (see below), whose sum is σ = 146038464. Its totient is φ = 42125760.

The previous prime is 81092777. The next prime is 81092783. The reversal of 81092781 is 18729018.

It is not a de Polignac number, because 81092781 - 2² = 81092777 is a prime.

It is a super-2 number, since 2×81092781² = 13152078260627922, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81092783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 57816 + ... + 59201.

It is an arithmetic number, because the mean of its divisors is an integer number (6084936).

Almost surely, 2^81092781 is an apocalyptic number.

It is an amenable number.

81092781 is a deficient number, since it is larger than the sum of its proper divisors (64945683).

81092781 is a wasteful number, since it uses less digits than its factorization.

81092781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117041 (or 117038 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 81092781 is about 9005.1530247964. The cubic root of 81092781 is about 432.8400097317.

The spelling of 81092781 in words is "eighty-one million, ninety-two thousand, seven hundred eighty-one".