19985621 has 2 divisors, whose sum is σ = 19985622. Its totient is φ = 19985620.

The previous prime is 19985617. The next prime is 19985627. The reversal of 19985621 is 12658991.

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., 19704721 + 280900 = 4439^2 + 530^2 .

It is an emirp because it is prime and its reverse (12658991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19985621 - 2² = 19985617 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19985627) 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, 9992810 + 9992811.

It is an arithmetic number, because the mean of its divisors is an integer number (9992811).

Almost surely, 2^19985621 is an apocalyptic number.

It is an amenable number.

19985621 is a deficient number, since it is larger than the sum of its proper divisors (1).

19985621 is an equidigital number, since it uses as much as digits as its factorization.

19985621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38880, while the sum is 41.

The square root of 19985621 is about 4470.5280448734. The cubic root of 19985621 is about 271.3766950456.

The spelling of 19985621 in words is "nineteen million, nine hundred eighty-five thousand, six hundred twenty-one".