81974781 has 16 divisors (see below), whose sum is σ = 138793600. Its totient is φ = 46842624.

The previous prime is 81974771. The next prime is 81974807. The reversal of 81974781 is 18747918.

It is not a de Polignac number, because 81974781 - 2⁷ = 81974653 is a prime.

It is a super-2 number, since 2×81974781² = 13439729439995922, 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 (81974741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 216676 + ... + 217053.

It is an arithmetic number, because the mean of its divisors is an integer number (8674600).

Almost surely, 2^81974781 is an apocalyptic number.

It is an amenable number.

81974781 is a deficient number, since it is larger than the sum of its proper divisors (56818819).

81974781 is a wasteful number, since it uses less digits than its factorization.

81974781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433745 (or 433739 counting only the distinct ones).

The product of its digits is 112896, while the sum is 45.

The square root of 81974781 is about 9053.9925447285. The cubic root of 81974781 is about 434.4036060108.

The spelling of 81974781 in words is "eighty-one million, nine hundred seventy-four thousand, seven hundred eighty-one".