81697731 has 8 divisors (see below), whose sum is σ = 110422800. Its totient is φ = 53718912.

The previous prime is 81697709. The next prime is 81697747. The reversal of 81697731 is 13779618.

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

It is not a de Polignac number, because 81697731 - 2¹¹ = 81695683 is a prime.

It is a super-2 number, since 2×81697731² = 13349038501096722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81697331) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 186306 + ... + 186743.

It is an arithmetic number, because the mean of its divisors is an integer number (13802850).

Almost surely, 2^81697731 is an apocalyptic number.

81697731 is a deficient number, since it is larger than the sum of its proper divisors (28725069).

81697731 is a wasteful number, since it uses less digits than its factorization.

81697731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 373125.

The product of its digits is 63504, while the sum is 42.

The square root of 81697731 is about 9038.6797155337. The cubic root of 81697731 is about 433.9136693227.

It can be divided in two parts, 81697 and 731, that added together give a palindrome (82428).

The spelling of 81697731 in words is "eighty-one million, six hundred ninety-seven thousand, seven hundred thirty-one".