81261281 has 2 divisors, whose sum is σ = 81261282. Its totient is φ = 81261280.

The previous prime is 81261251. The next prime is 81261289. The reversal of 81261281 is 18216218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 72165025 + 9096256 = 8495^2 + 3016^2 .

It is a cyclic number.

It is not a de Polignac number, because 81261281 - 2¹⁴ = 81244897 is a prime.

It is a super-2 number, since 2×81261281² = 13206791579521922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81261289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40630640 + 40630641.

It is an arithmetic number, because the mean of its divisors is an integer number (40630641).

Almost surely, 2^81261281 is an apocalyptic number.

It is an amenable number.

81261281 is a deficient number, since it is larger than the sum of its proper divisors (1).

81261281 is an equidigital number, since it uses as much as digits as its factorization.

81261281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 29.

The square root of 81261281 is about 9014.5039242323. The cubic root of 81261281 is about 433.1395969599.

Adding to 81261281 its reverse (18216218), we get a palindrome (99477499).

The spelling of 81261281 in words is "eighty-one million, two hundred sixty-one thousand, two hundred eighty-one".