81624509 has 2 divisors, whose sum is σ = 81624510. Its totient is φ = 81624508.

The previous prime is 81624461. The next prime is 81624523. The reversal of 81624509 is 90542618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 78818884 + 2805625 = 8878^2 + 1675^2 .

It is a cyclic number.

It is not a de Polignac number, because 81624509 - 2¹⁶ = 81558973 is a prime.

It is a Chen prime.

It is equal to p_4758821 and since 81624509 and 4758821 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81621509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40812254 + 40812255.

It is an arithmetic number, because the mean of its divisors is an integer number (40812255).

Almost surely, 2^81624509 is an apocalyptic number.

It is an amenable number.

81624509 is a deficient number, since it is larger than the sum of its proper divisors (1).

81624509 is an equidigital number, since it uses as much as digits as its factorization.

81624509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 81624509 is about 9034.6283266109. The cubic root of 81624509 is about 433.7839981434.

The spelling of 81624509 in words is "eighty-one million, six hundred twenty-four thousand, five hundred nine".