81516641 has 2 divisors, whose sum is σ = 81516642. Its totient is φ = 81516640.

The previous prime is 81516637. The next prime is 81516653. The reversal of 81516641 is 14661518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61230625 + 20286016 = 7825^2 + 4504^2 .

It is a cyclic number.

It is not a de Polignac number, because 81516641 - 2² = 81516637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81516598 and 81516607.

It is not a weakly prime, because it can be changed into another prime (81516671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40758320 + 40758321.

It is an arithmetic number, because the mean of its divisors is an integer number (40758321).

Almost surely, 2^81516641 is an apocalyptic number.

It is an amenable number.

81516641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81516641 is an equidigital number, since it uses as much as digits as its factorization.

81516641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5760, while the sum is 32.

The square root of 81516641 is about 9028.6566553392. The cubic root of 81516641 is about 433.5928299111.

The spelling of 81516641 in words is "eighty-one million, five hundred sixteen thousand, six hundred forty-one".