81653281 has 2 divisors, whose sum is σ = 81653282. Its totient is φ = 81653280.

The previous prime is 81653267. The next prime is 81653309. The reversal of 81653281 is 18235618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41216400 + 40436881 = 6420^2 + 6359^2 .

It is a cyclic number.

It is not a de Polignac number, because 81653281 - 2¹¹ = 81651233 is a prime.

It is a super-2 number, since 2×81653281² = 13334516596129922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81653251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40826640 + 40826641.

It is an arithmetic number, because the mean of its divisors is an integer number (40826641).

Almost surely, 2^81653281 is an apocalyptic number.

It is an amenable number.

81653281 is a deficient number, since it is larger than the sum of its proper divisors (1).

81653281 is an equidigital number, since it uses as much as digits as its factorization.

81653281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11520, while the sum is 34.

The square root of 81653281 is about 9036.2205041710. The cubic root of 81653281 is about 433.8349606430.

Adding to 81653281 its reverse (18235618), we get a palindrome (99888899).

The spelling of 81653281 in words is "eighty-one million, six hundred fifty-three thousand, two hundred eighty-one".