81327661 has 2 divisors, whose sum is σ = 81327662. Its totient is φ = 81327660.

The previous prime is 81327647. The next prime is 81327679. The reversal of 81327661 is 16672318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80460900 + 866761 = 8970^2 + 931^2 .

It is a cyclic number.

It is not a de Polignac number, because 81327661 - 2¹¹ = 81325613 is a prime.

It is a super-2 number, since 2×81327661² = 13228376887461842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81327611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40663830 + 40663831.

It is an arithmetic number, because the mean of its divisors is an integer number (40663831).

Almost surely, 2^81327661 is an apocalyptic number.

It is an amenable number.

81327661 is a deficient number, since it is larger than the sum of its proper divisors (1).

81327661 is an equidigital number, since it uses as much as digits as its factorization.

81327661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12096, while the sum is 34.

The square root of 81327661 is about 9018.1850169532. The cubic root of 81327661 is about 433.2575046145.

Adding to 81327661 its reverse (16672318), we get a palindrome (97999979).

The spelling of 81327661 in words is "eighty-one million, three hundred twenty-seven thousand, six hundred sixty-one".