81870109 has 2 divisors, whose sum is σ = 81870110. Its totient is φ = 81870108.

The previous prime is 81870091. The next prime is 81870119. The reversal of 81870109 is 90107818.

Together with previous prime (81870091) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80604484 + 1265625 = 8978^2 + 1125^2 .

It is a cyclic number.

It is not a de Polignac number, because 81870109 - 2⁵ = 81870077 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81870119) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40935054 + 40935055.

It is an arithmetic number, because the mean of its divisors is an integer number (40935055).

Almost surely, 2^81870109 is an apocalyptic number.

It is an amenable number.

81870109 is a deficient number, since it is larger than the sum of its proper divisors (1).

81870109 is an equidigital number, since it uses as much as digits as its factorization.

81870109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 34.

The square root of 81870109 is about 9048.2102650193. The cubic root of 81870109 is about 434.2186334268.

The spelling of 81870109 in words is "eighty-one million, eight hundred seventy thousand, one hundred nine".