81669913 has 8 divisors (see below), whose sum is σ = 88824456. Its totient is φ = 74640000.

The previous prime is 81669899. The next prime is 81669937. The reversal of 81669913 is 31996618.

It can be written as a sum of positive squares in 4 ways, for example, as 4721929 + 76947984 = 2173^2 + 8772^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81669913 - 2¹³ = 81661721 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81669913.

It is not an unprimeable number, because it can be changed into a prime (81669953) 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, 29788 + ... + 32413.

It is an arithmetic number, because the mean of its divisors is an integer number (11103057).

Almost surely, 2^81669913 is an apocalyptic number.

It is an amenable number.

81669913 is a deficient number, since it is larger than the sum of its proper divisors (7154543).

81669913 is a wasteful number, since it uses less digits than its factorization.

81669913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62315.

The product of its digits is 69984, while the sum is 43.

The square root of 81669913 is about 9037.1407535791. The cubic root of 81669913 is about 433.8644146675.

The spelling of 81669913 in words is "eighty-one million, six hundred sixty-nine thousand, nine hundred thirteen".