19973621 has 2 divisors, whose sum is σ = 19973622. Its totient is φ = 19973620.

The previous prime is 19973587. The next prime is 19973651. The reversal of 19973621 is 12637991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13140625 + 6832996 = 3625^2 + 2614^2 .

It is an emirp because it is prime and its reverse (12637991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19973621 - 2¹⁸ = 19711477 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 (19973651) 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, 9986810 + 9986811.

It is an arithmetic number, because the mean of its divisors is an integer number (9986811).

Almost surely, 2^19973621 is an apocalyptic number.

It is an amenable number.

19973621 is a deficient number, since it is larger than the sum of its proper divisors (1).

19973621 is an equidigital number, since it uses as much as digits as its factorization.

19973621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20412, while the sum is 38.

The square root of 19973621 is about 4469.1857200166. The cubic root of 19973621 is about 271.3223697829.

The spelling of 19973621 in words is "nineteen million, nine hundred seventy-three thousand, six hundred twenty-one".