81743821 has 2 divisors, whose sum is σ = 81743822. Its totient is φ = 81743820.

The previous prime is 81743801. The next prime is 81743897. The reversal of 81743821 is 12834718.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 53494596 + 28249225 = 7314^2 + 5315^2 .

It is a cyclic number.

It is not a de Polignac number, because 81743821 - 2⁹ = 81743309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81743801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40871910 + 40871911.

It is an arithmetic number, because the mean of its divisors is an integer number (40871911).

Almost surely, 2^81743821 is an apocalyptic number.

It is an amenable number.

81743821 is a deficient number, since it is larger than the sum of its proper divisors (1).

81743821 is an equidigital number, since it uses as much as digits as its factorization.

81743821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10752, while the sum is 34.

The square root of 81743821 is about 9041.2289540748. The cubic root of 81743821 is about 433.9952518469.

The spelling of 81743821 in words is "eighty-one million, seven hundred forty-three thousand, eight hundred twenty-one".