81947757 has 8 divisors (see below), whose sum is σ = 109391776. Its totient is φ = 54567792.

The previous prime is 81947753. The next prime is 81947771. The reversal of 81947757 is 75774918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81947757 - 2² = 81947753 is a prime.

It is the 9053-rd Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81947753) by changing a digit.

It is a nontrivial repunit in base 9052.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12943 + ... + 18204.

It is an arithmetic number, because the mean of its divisors is an integer number (13673972).

Almost surely, 2^81947757 is an apocalyptic number.

It is an amenable number.

81947757 is a deficient number, since it is larger than the sum of its proper divisors (27444019).

81947757 is a wasteful number, since it uses less digits than its factorization.

81947757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32027.

The product of its digits is 493920, while the sum is 48.

The square root of 81947757 is about 9052.5000414250. The cubic root of 81947757 is about 434.3558652579.

It can be divided in two parts, 8194 and 7757, that added together give a palindrome (15951).

The spelling of 81947757 in words is "eighty-one million, nine hundred forty-seven thousand, seven hundred fifty-seven".