81808637 has 2 divisors, whose sum is σ = 81808638. Its totient is φ = 81808636.

The previous prime is 81808619. The next prime is 81808651. The reversal of 81808637 is 73680818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73170916 + 8637721 = 8554^2 + 2939^2 .

It is a cyclic number.

It is not a de Polignac number, because 81808637 - 2¹⁰ = 81807613 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 81808594 and 81808603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81808697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40904318 + 40904319.

It is an arithmetic number, because the mean of its divisors is an integer number (40904319).

Almost surely, 2^81808637 is an apocalyptic number.

It is an amenable number.

81808637 is a deficient number, since it is larger than the sum of its proper divisors (1).

81808637 is an equidigital number, since it uses as much as digits as its factorization.

81808637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 64512, while the sum is 41.

The square root of 81808637 is about 9044.8127122677. The cubic root of 81808637 is about 434.1099288313.

The spelling of 81808637 in words is "eighty-one million, eight hundred eight thousand, six hundred thirty-seven".