1820721943 has 2 divisors, whose sum is σ = 1820721944. Its totient is φ = 1820721942.

The previous prime is 1820721907. The next prime is 1820721997. The reversal of 1820721943 is 3491270281.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1820721943 - 2⁹ = 1820721431 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1820724943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910360971 + 910360972.

It is an arithmetic number, because the mean of its divisors is an integer number (910360972).

Almost surely, 2^1820721943 is an apocalyptic number.

1820721943 is a deficient number, since it is larger than the sum of its proper divisors (1).

1820721943 is an equidigital number, since it uses as much as digits as its factorization.

1820721943 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 1820721943 is about 42669.9184789472. The cubic root of 1820721943 is about 1221.0905645327.

The spelling of 1820721943 in words is "one billion, eight hundred twenty million, seven hundred twenty-one thousand, nine hundred forty-three".