999998621 has 2 divisors, whose sum is σ = 999998622. Its totient is φ = 999998620.

The previous prime is 999998617. The next prime is 999998627. The reversal of 999998621 is 126899999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 757075225 + 242923396 = 27515^2 + 15586^2 .

It is an emirp because it is prime and its reverse (126899999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 999998621 - 2² = 999998617 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (999998627) 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, 499999310 + 499999311.

It is an arithmetic number, because the mean of its divisors is an integer number (499999311).

Almost surely, 2^999998621 is an apocalyptic number.

It is an amenable number.

999998621 is a deficient number, since it is larger than the sum of its proper divisors (1).

999998621 is an equidigital number, since it uses as much as digits as its factorization.

999998621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5668704, while the sum is 62.

The square root of 999998621 is about 31622.7547977718. The cubic root of 999998621 is about 999.9995403331. Note that the first 3 decimals are identical.

The spelling of 999998621 in words is "nine hundred ninety-nine million, nine hundred ninety-eight thousand, six hundred twenty-one".