1998337721 has 2 divisors, whose sum is σ = 1998337722. Its totient is φ = 1998337720.

The previous prime is 1998337687. The next prime is 1998337739. The reversal of 1998337721 is 1277338991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1804125625 + 194212096 = 42475^2 + 13936^2 .

It is a cyclic number.

It is not a de Polignac number, because 1998337721 - 2¹⁴ = 1998321337 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1998337721.

It is not a weakly prime, because it can be changed into another prime (1998337741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 999168860 + 999168861.

It is an arithmetic number, because the mean of its divisors is an integer number (999168861).

Almost surely, 2^1998337721 is an apocalyptic number.

It is an amenable number.

1998337721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1998337721 is an equidigital number, since it uses as much as digits as its factorization.

1998337721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 571536, while the sum is 50.

The square root of 1998337721 is about 44702.7708425328. The cubic root of 1998337721 is about 1259.5718964281.

The spelling of 1998337721 in words is "one billion, nine hundred ninety-eight million, three hundred thirty-seven thousand, seven hundred twenty-one".