81521611 has 2 divisors, whose sum is σ = 81521612. Its totient is φ = 81521610.

The previous prime is 81521567. The next prime is 81521617. The reversal of 81521611 is 11612518.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81521611 - 2⁷ = 81521483 is a prime.

It is not a weakly prime, because it can be changed into another prime (81521617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760805 + 40760806.

It is an arithmetic number, because the mean of its divisors is an integer number (40760806).

Almost surely, 2^81521611 is an apocalyptic number.

81521611 is a deficient number, since it is larger than the sum of its proper divisors (1).

81521611 is an equidigital number, since it uses as much as digits as its factorization.

81521611 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 25.

The square root of 81521611 is about 9028.9318858877. The cubic root of 81521611 is about 433.6016416602.

The spelling of 81521611 in words is "eighty-one million, five hundred twenty-one thousand, six hundred eleven".