81860991 has 16 divisors (see below), whose sum is σ = 112565376. Its totient is φ = 52890656.

The previous prime is 81860971. The next prime is 81861011. The reversal of 81860991 is 19906818.

It is an interprime number because it is at equal distance from previous prime (81860971) and next prime (81861011).

It is a cyclic number.

It is not a de Polignac number, because 81860991 - 2⁹ = 81860479 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81860951) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10096 + ... + 16298.

It is an arithmetic number, because the mean of its divisors is an integer number (7035336).

Almost surely, 2^81860991 is an apocalyptic number.

81860991 is a deficient number, since it is larger than the sum of its proper divisors (30704385).

81860991 is a wasteful number, since it uses less digits than its factorization.

81860991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6342.

The product of its (nonzero) digits is 31104, while the sum is 42.

The square root of 81860991 is about 9047.7063944405. The cubic root of 81860991 is about 434.2025129625.

The spelling of 81860991 in words is "eighty-one million, eight hundred sixty thousand, nine hundred ninety-one".