81415181 has 2 divisors, whose sum is σ = 81415182. Its totient is φ = 81415180.

The previous prime is 81415163. The next prime is 81415183. The reversal of 81415181 is 18151418.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79370281 + 2044900 = 8909^2 + 1430^2 .

It is a cyclic number.

It is not a de Polignac number, because 81415181 - 2¹⁴ = 81398797 is a prime.

It is a super-2 number, since 2×81415181² = 13256863394525522, which contains 22 as substring.

Together with 81415183, it forms a pair of twin primes.

It is a Chen prime.

It is a pancake number, because a pancake can be divided into 81415181 parts by 12760 straight cuts.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81415183) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40707590 + 40707591.

It is an arithmetic number, because the mean of its divisors is an integer number (40707591).

Almost surely, 2^81415181 is an apocalyptic number.

It is an amenable number.

81415181 is a deficient number, since it is larger than the sum of its proper divisors (1).

81415181 is an equidigital number, since it uses as much as digits as its factorization.

81415181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1280, while the sum is 29.

The square root of 81415181 is about 9023.0361298179. The cubic root of 81415181 is about 433.4128642323.

Adding to 81415181 its reverse (18151418), we get a palindrome (99566599).

The spelling of 81415181 in words is "eighty-one million, four hundred fifteen thousand, one hundred eighty-one".