81645073 has 2 divisors, whose sum is σ = 81645074. Its totient is φ = 81645072.

The previous prime is 81645059. The next prime is 81645077. The reversal of 81645073 is 37054618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70274689 + 11370384 = 8383^2 + 3372^2 .

It is a cyclic number.

It is not a de Polignac number, because 81645073 - 2⁹ = 81644561 is a prime.

It is not a weakly prime, because it can be changed into another prime (81645077) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40822536 + 40822537.

It is an arithmetic number, because the mean of its divisors is an integer number (40822537).

Almost surely, 2^81645073 is an apocalyptic number.

It is an amenable number.

81645073 is a deficient number, since it is larger than the sum of its proper divisors (1).

81645073 is an equidigital number, since it uses as much as digits as its factorization.

81645073 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20160, while the sum is 34.

The square root of 81645073 is about 9035.7663205729. The cubic root of 81645073 is about 433.8204234167.

The spelling of 81645073 in words is "eighty-one million, six hundred forty-five thousand, seventy-three".