81981747 has 16 divisors (see below), whose sum is σ = 122078880. Its totient is φ = 54373536.

The previous prime is 81981719. The next prime is 81981761. The reversal of 81981747 is 74718918.

It is not a de Polignac number, because 81981747 - 2²² = 77787443 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81981707) 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, 2388 + ... + 13025.

It is an arithmetic number, because the mean of its divisors is an integer number (7629930).

Almost surely, 2^81981747 is an apocalyptic number.

81981747 is a deficient number, since it is larger than the sum of its proper divisors (40097133).

81981747 is a wasteful number, since it uses less digits than its factorization.

81981747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15619 (or 15613 counting only the distinct ones).

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

The square root of 81981747 is about 9054.3772287220. The cubic root of 81981747 is about 434.4159104853.

It can be divided in two parts, 81981 and 747, that added together give a palindrome (82728).

The spelling of 81981747 in words is "eighty-one million, nine hundred eighty-one thousand, seven hundred forty-seven".