81259891 has 2 divisors, whose sum is σ = 81259892. Its totient is φ = 81259890.

The previous prime is 81259879. The next prime is 81259921. The reversal of 81259891 is 19895218.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81259891 - 2¹¹ = 81257843 is a prime.

It is not a weakly prime, because it can be changed into another prime (81259831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40629945 + 40629946.

It is an arithmetic number, because the mean of its divisors is an integer number (40629946).

Almost surely, 2^81259891 is an apocalyptic number.

81259891 is a deficient number, since it is larger than the sum of its proper divisors (1).

81259891 is an equidigital number, since it uses as much as digits as its factorization.

81259891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 51840, while the sum is 43.

The square root of 81259891 is about 9014.4268259274. The cubic root of 81259891 is about 433.1371272824.

The spelling of 81259891 in words is "eighty-one million, two hundred fifty-nine thousand, eight hundred ninety-one".