81608981 has 2 divisors, whose sum is σ = 81608982. Its totient is φ = 81608980.

The previous prime is 81608953. The next prime is 81608999. The reversal of 81608981 is 18980618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60310756 + 21298225 = 7766^2 + 4615^2 .

It is a cyclic number.

It is not a de Polignac number, because 81608981 - 2¹⁴ = 81592597 is a prime.

It is a super-2 number, since 2×81608981² = 13320051559716722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is a weakly prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40804490 + 40804491.

It is an arithmetic number, because the mean of its divisors is an integer number (40804491).

Almost surely, 2^81608981 is an apocalyptic number.

It is an amenable number.

81608981 is a deficient number, since it is larger than the sum of its proper divisors (1).

81608981 is an equidigital number, since it uses as much as digits as its factorization.

81608981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27648, while the sum is 41.

The square root of 81608981 is about 9033.7689255371. The cubic root of 81608981 is about 433.7564891465.

The spelling of 81608981 in words is "eighty-one million, six hundred eight thousand, nine hundred eighty-one".