81591863 has 8 divisors (see below), whose sum is σ = 82977408. Its totient is φ = 80211384.

The previous prime is 81591827. The next prime is 81591869. The reversal of 81591863 is 36819518.

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 81591863 - 2⁶ = 81591799 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 81591863.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81591869) 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, 44870 + ... + 46652.

It is an arithmetic number, because the mean of its divisors is an integer number (10372176).

Almost surely, 2^81591863 is an apocalyptic number.

81591863 is a deficient number, since it is larger than the sum of its proper divisors (1385545).

81591863 is a wasteful number, since it uses less digits than its factorization.

81591863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2533.

The product of its digits is 51840, while the sum is 41.

The square root of 81591863 is about 9032.8214307602. The cubic root of 81591863 is about 433.7261593033.

The spelling of 81591863 in words is "eighty-one million, five hundred ninety-one thousand, eight hundred sixty-three".