81210881 has 2 divisors, whose sum is σ = 81210882. Its totient is φ = 81210880.

The previous prime is 81210823. The next prime is 81210911. The reversal of 81210881 is 18801218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 76300225 + 4910656 = 8735^2 + 2216^2 .

It is a cyclic number.

It is not a de Polignac number, because 81210881 - 2¹⁴ = 81194497 is a prime.

It is a super-2 number, since 2×81210881² = 13190414385592322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81210281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40605440 + 40605441.

It is an arithmetic number, because the mean of its divisors is an integer number (40605441).

Almost surely, 2^81210881 is an apocalyptic number.

It is an amenable number.

81210881 is a deficient number, since it is larger than the sum of its proper divisors (1).

81210881 is an equidigital number, since it uses as much as digits as its factorization.

81210881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1024, while the sum is 29.

The square root of 81210881 is about 9011.7079957131. The cubic root of 81210881 is about 433.0500309322.

The spelling of 81210881 in words is "eighty-one million, two hundred ten thousand, eight hundred eighty-one".