81908881 has 2 divisors, whose sum is σ = 81908882. Its totient is φ = 81908880.

The previous prime is 81908863. The next prime is 81908887. The reversal of 81908881 is 18880918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 79923600 + 1985281 = 8940^2 + 1409^2 .

It is a cyclic number.

It is not a de Polignac number, because 81908881 - 2¹⁷ = 81777809 is a prime.

It is a super-2 number, since 2×81908881² = 13418129573344322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81908887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40954440 + 40954441.

It is an arithmetic number, because the mean of its divisors is an integer number (40954441).

Almost surely, 2^81908881 is an apocalyptic number.

It is an amenable number.

81908881 is a deficient number, since it is larger than the sum of its proper divisors (1).

81908881 is an equidigital number, since it uses as much as digits as its factorization.

81908881 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36864, while the sum is 43.

The square root of 81908881 is about 9050.3525345701. The cubic root of 81908881 is about 434.2871682808.

It can be divided in two parts, 8190 and 8881, that added together give a palindrome (17071).

The spelling of 81908881 in words is "eighty-one million, nine hundred eight thousand, eight hundred eighty-one".