81257117 has 2 divisors, whose sum is σ = 81257118. Its totient is φ = 81257116.

The previous prime is 81257087. The next prime is 81257149. The reversal of 81257117 is 71175218.

It is an a-pointer prime, because the next prime (81257149) can be obtained adding 81257117 to its sum of digits (32).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63457156 + 17799961 = 7966^2 + 4219^2 .

It is a cyclic number.

It is not a de Polignac number, because 81257117 - 2¹⁶ = 81191581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81257017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40628558 + 40628559.

It is an arithmetic number, because the mean of its divisors is an integer number (40628559).

Almost surely, 2^81257117 is an apocalyptic number.

It is an amenable number.

81257117 is a deficient number, since it is larger than the sum of its proper divisors (1).

81257117 is an equidigital number, since it uses as much as digits as its factorization.

81257117 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3920, while the sum is 32.

The square root of 81257117 is about 9014.2729601449. The cubic root of 81257117 is about 433.1321985037.

The spelling of 81257117 in words is "eighty-one million, two hundred fifty-seven thousand, one hundred seventeen".