81642241 has 2 divisors, whose sum is σ = 81642242. Its totient is φ = 81642240.

The previous prime is 81642233. The next prime is 81642257. The reversal of 81642241 is 14224618.

81642241 is nontrivially palindromic in base 9.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70560000 + 11082241 = 8400^2 + 3329^2 .

It is a cyclic number.

It is not a de Polignac number, because 81642241 - 2³ = 81642233 is a prime.

It is not a weakly prime, because it can be changed into another prime (81642541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40821120 + 40821121.

It is an arithmetic number, because the mean of its divisors is an integer number (40821121).

Almost surely, 2^81642241 is an apocalyptic number.

It is an amenable number.

81642241 is a deficient number, since it is larger than the sum of its proper divisors (1).

81642241 is an equidigital number, since it uses as much as digits as its factorization.

81642241 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3072, while the sum is 28.

The square root of 81642241 is about 9035.6096086540. The cubic root of 81642241 is about 433.8154074225.

Adding to 81642241 its reverse (14224618), we get a palindrome (95866859).

The spelling of 81642241 in words is "eighty-one million, six hundred forty-two thousand, two hundred forty-one".