81697529 has 4 divisors (see below), whose sum is σ = 86503284. Its totient is φ = 76891776.

The previous prime is 81697519. The next prime is 81697537. The reversal of 81697529 is 92579618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 92579618 = 2 ⋅46289809.

It can be written as a sum of positive squares in 2 ways, for example, as 29106025 + 52591504 = 5395^2 + 7252^2 .

It is a cyclic number.

It is not a de Polignac number, because 81697529 - 2¹² = 81693433 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81697519) 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 3 ways as a sum of consecutive naturals, for example, 2402852 + ... + 2402885.

It is an arithmetic number, because the mean of its divisors is an integer number (21625821).

Almost surely, 2^81697529 is an apocalyptic number.

It is an amenable number.

81697529 is a deficient number, since it is larger than the sum of its proper divisors (4805755).

81697529 is a wasteful number, since it uses less digits than its factorization.

81697529 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4805754.

The product of its digits is 272160, while the sum is 47.

The square root of 81697529 is about 9038.6685413284. The cubic root of 81697529 is about 433.9133117011.

The spelling of 81697529 in words is "eighty-one million, six hundred ninety-seven thousand, five hundred twenty-nine".