81261617 has 2 divisors, whose sum is σ = 81261618. Its totient is φ = 81261616.

The previous prime is 81261589. The next prime is 81261619. The reversal of 81261617 is 71616218.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 42523441 + 38738176 = 6521^2 + 6224^2 .

It is a cyclic number.

It is not a de Polignac number, because 81261617 - 2¹⁰ = 81260593 is a prime.

Together with 81261619, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81261619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40630808 + 40630809.

It is an arithmetic number, because the mean of its divisors is an integer number (40630809).

Almost surely, 2^81261617 is an apocalyptic number.

It is an amenable number.

81261617 is a deficient number, since it is larger than the sum of its proper divisors (1).

81261617 is an equidigital number, since it uses as much as digits as its factorization.

81261617 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 32.

The square root of 81261617 is about 9014.5225608459. The cubic root of 81261617 is about 433.1401939425.

The spelling of 81261617 in words is "eighty-one million, two hundred sixty-one thousand, six hundred seventeen".