71505821 has 2 divisors, whose sum is σ = 71505822. Its totient is φ = 71505820.

The previous prime is 71505799. The next prime is 71505839. The reversal of 71505821 is 12850517.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 57592921 + 13912900 = 7589^2 + 3730^2 .

It is a cyclic number.

It is not a de Polignac number, because 71505821 - 2¹⁸ = 71243677 is a prime.

It is a super-2 number, since 2×71505821² = 10226164873768082, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71505121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35752910 + 35752911.

It is an arithmetic number, because the mean of its divisors is an integer number (35752911).

Almost surely, 2^71505821 is an apocalyptic number.

It is an amenable number.

71505821 is a deficient number, since it is larger than the sum of its proper divisors (1).

71505821 is an equidigital number, since it uses as much as digits as its factorization.

71505821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2800, while the sum is 29.

The square root of 71505821 is about 8456.1114585843. Note that the first 3 decimals coincide. The cubic root of 71505821 is about 415.0627881967.

The spelling of 71505821 in words is "seventy-one million, five hundred five thousand, eight hundred twenty-one".