81907569 has 12 divisors (see below), whose sum is σ = 118389492. Its totient is φ = 54568800.

The previous prime is 81907559. The next prime is 81907589. The reversal of 81907569 is 96570918.

81907569 is a `hidden beast` number, since 81 + 9 + 0 + 7 + 569 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 23155344 + 58752225 = 4812^2 + 7665^2 .

It is not a de Polignac number, because 81907569 - 2¹¹ = 81905521 is a prime.

It is a super-2 number, since 2×81907569² = 13417699718979522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81907519) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 24159 + ... + 27339.

It is an arithmetic number, because the mean of its divisors is an integer number (9865791).

Almost surely, 2^81907569 is an apocalyptic number.

It is an amenable number.

81907569 is a deficient number, since it is larger than the sum of its proper divisors (36481923).

81907569 is a wasteful number, since it uses less digits than its factorization.

81907569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6048 (or 6045 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The square root of 81907569 is about 9050.2800509156. The cubic root of 81907569 is about 434.2848494935.

The spelling of 81907569 in words is "eighty-one million, nine hundred seven thousand, five hundred sixty-nine".