81220541 has 2 divisors, whose sum is σ = 81220542. Its totient is φ = 81220540.

The previous prime is 81220537. The next prime is 81220553. The reversal of 81220541 is 14502218.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 63664441 + 17556100 = 7979^2 + 4190^2 .

It is a cyclic number.

It is not a de Polignac number, because 81220541 - 2² = 81220537 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81220591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40610270 + 40610271.

It is an arithmetic number, because the mean of its divisors is an integer number (40610271).

Almost surely, 2^81220541 is an apocalyptic number.

It is an amenable number.

81220541 is a deficient number, since it is larger than the sum of its proper divisors (1).

81220541 is an equidigital number, since it uses as much as digits as its factorization.

81220541 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 81220541 is about 9012.2439492060. The cubic root of 81220541 is about 433.0672006242.

Adding to 81220541 its reverse (14502218), we get a palindrome (95722759).

The spelling of 81220541 in words is "eighty-one million, two hundred twenty thousand, five hundred forty-one".