81723773 has 2 divisors, whose sum is σ = 81723774. Its totient is φ = 81723772.

The previous prime is 81723757. The next prime is 81723797. The reversal of 81723773 is 37732718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 75307684 + 6416089 = 8678^2 + 2533^2 .

It is a cyclic number.

It is not a de Polignac number, because 81723773 - 2⁴ = 81723757 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81743773) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40861886 + 40861887.

It is an arithmetic number, because the mean of its divisors is an integer number (40861887).

Almost surely, 2^81723773 is an apocalyptic number.

It is an amenable number.

81723773 is a deficient number, since it is larger than the sum of its proper divisors (1).

81723773 is an equidigital number, since it uses as much as digits as its factorization.

81723773 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 49392, while the sum is 38.

The square root of 81723773 is about 9040.1201872541. The cubic root of 81723773 is about 433.9597692539.

The spelling of 81723773 in words is "eighty-one million, seven hundred twenty-three thousand, seven hundred seventy-three".