81959569 has 2 divisors, whose sum is σ = 81959570. Its totient is φ = 81959568.

The previous prime is 81959513. The next prime is 81959593. The reversal of 81959569 is 96595918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77228944 + 4730625 = 8788^2 + 2175^2 .

It is a cyclic number.

It is not a de Polignac number, because 81959569 - 2¹³ = 81951377 is a prime.

It is a super-2 number, since 2×81959569² = 13434741901331522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81956569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40979784 + 40979785.

It is an arithmetic number, because the mean of its divisors is an integer number (40979785).

Almost surely, 2^81959569 is an apocalyptic number.

It is an amenable number.

81959569 is a deficient number, since it is larger than the sum of its proper divisors (1).

81959569 is an equidigital number, since it uses as much as digits as its factorization.

81959569 is an evil number, because the sum of its binary digits is even.

The product of its digits is 874800, while the sum is 52.

The square root of 81959569 is about 9053.1524343733. The cubic root of 81959569 is about 434.3767336956.

It can be divided in two parts, 81959 and 569, that added together give a palindrome (82528).

The spelling of 81959569 in words is "eighty-one million, nine hundred fifty-nine thousand, five hundred sixty-nine".