81689261 has 8 divisors (see below), whose sum is σ = 87321024. Its totient is φ = 76230880.

The previous prime is 81689213. The next prime is 81689269. The reversal of 81689261 is 16298618.

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 81689261 - 2¹⁰ = 81688237 is a prime.

It is a super-2 number, since 2×81689261² = 13346270725452242, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689269) 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 7 ways as a sum of consecutive naturals, for example, 42371 + ... + 44256.

It is an arithmetic number, because the mean of its divisors is an integer number (10915128).

Almost surely, 2^81689261 is an apocalyptic number.

It is an amenable number.

81689261 is a deficient number, since it is larger than the sum of its proper divisors (5631763).

81689261 is a wasteful number, since it uses less digits than its factorization.

81689261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86691.

The product of its digits is 41472, while the sum is 41.

The square root of 81689261 is about 9038.2111615076. The cubic root of 81689261 is about 433.8986734930.

The spelling of 81689261 in words is "eighty-one million, six hundred eighty-nine thousand, two hundred sixty-one".