81690586 has 4 divisors (see below), whose sum is σ = 122535882. Its totient is φ = 40845292.

The previous prime is 81690571. The next prime is 81690589. The reversal of 81690586 is 68509618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 68509618 = 2 ⋅34254809.

It can be written as a sum of positive squares in only one way, i.e., 69405561 + 12285025 = 8331^2 + 3505^2 .

It is not an unprimeable number, because it can be changed into a prime (81690589) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20422645 + ... + 20422648.

Almost surely, 2^81690586 is an apocalyptic number.

81690586 is a deficient number, since it is larger than the sum of its proper divisors (40845296).

81690586 is a wasteful number, since it uses less digits than its factorization.

81690586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40845295.

The product of its (nonzero) digits is 103680, while the sum is 43.

The square root of 81690586 is about 9038.2844611132. The cubic root of 81690586 is about 433.9010194261.

The spelling of 81690586 in words is "eighty-one million, six hundred ninety thousand, five hundred eighty-six".