81186981 has 16 divisors (see below), whose sum is σ = 114777600. Its totient is φ = 50902128.

The previous prime is 81186961. The next prime is 81186983. The reversal of 81186981 is 18968118.

It is not a de Polignac number, because 81186981 - 2¹⁰ = 81185957 is a prime.

It is a super-2 number, since 2×81186981² = 13182651767788722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81186983) 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 15 ways as a sum of consecutive naturals, for example, 2800 + ... + 13046.

It is an arithmetic number, because the mean of its divisors is an integer number (7173600).

Almost surely, 2^81186981 is an apocalyptic number.

It is an amenable number.

81186981 is a deficient number, since it is larger than the sum of its proper divisors (33590619).

81186981 is a wasteful number, since it uses less digits than its factorization.

81186981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10408.

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

The square root of 81186981 is about 9010.3818454048. The cubic root of 81186981 is about 433.0075452001.

The spelling of 81186981 in words is "eighty-one million, one hundred eighty-six thousand, nine hundred eighty-one".