81859681 has 2 divisors, whose sum is σ = 81859682. Its totient is φ = 81859680.

The previous prime is 81859669. The next prime is 81859711. The reversal of 81859681 is 18695818.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 60699681 + 21160000 = 7791^2 + 4600^2 .

It is a cyclic number.

It is not a de Polignac number, because 81859681 - 2⁵ = 81859649 is a prime.

It is a super-2 number, since 2×81859681² = 13402014746843522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81859181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40929840 + 40929841.

It is an arithmetic number, because the mean of its divisors is an integer number (40929841).

Almost surely, 2^81859681 is an apocalyptic number.

It is an amenable number.

81859681 is a deficient number, since it is larger than the sum of its proper divisors (1).

81859681 is an equidigital number, since it uses as much as digits as its factorization.

81859681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 138240, while the sum is 46.

The square root of 81859681 is about 9047.6340001130. The cubic root of 81859681 is about 434.2001968072.

The spelling of 81859681 in words is "eighty-one million, eight hundred fifty-nine thousand, six hundred eighty-one".