999999997621 has 2 divisors, whose sum is σ = 999999997622. Its totient is φ = 999999997620.

The previous prime is 999999997603. The next prime is 999999997679. The reversal of 999999997621 is 126799999999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 729640556100 + 270359441521 = 854190^2 + 519961^2 .

It is a cyclic number.

It is not a de Polignac number, because 999999997621 - 2⁵ = 999999997589 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 (999999997721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499999998810 + 499999998811.

It is an arithmetic number, because the mean of its divisors is an integer number (499999998811).

Almost surely, 2^999999997621 is an apocalyptic number.

It is an amenable number.

999999997621 is a deficient number, since it is larger than the sum of its proper divisors (1).

999999997621 is an equidigital number, since it uses as much as digits as its factorization.

999999997621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3615924564, while the sum is 88.

The spelling of 999999997621 in words is "nine hundred ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-seven thousand, six hundred twenty-one".