81722891 has 2 divisors, whose sum is σ = 81722892. Its totient is φ = 81722890.

The previous prime is 81722827. The next prime is 81722897. The reversal of 81722891 is 19822718.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81722891 - 2⁶ = 81722827 is a prime.

It is not a weakly prime, because it can be changed into another prime (81722897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40861445 + 40861446.

It is an arithmetic number, because the mean of its divisors is an integer number (40861446).

Almost surely, 2^81722891 is an apocalyptic number.

81722891 is a deficient number, since it is larger than the sum of its proper divisors (1).

81722891 is an equidigital number, since it uses as much as digits as its factorization.

81722891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16128, while the sum is 38.

The square root of 81722891 is about 9040.0714045853. The cubic root of 81722891 is about 433.9582080848.

The spelling of 81722891 in words is "eighty-one million, seven hundred twenty-two thousand, eight hundred ninety-one".