19966021 has 2 divisors, whose sum is σ = 19966022. Its totient is φ = 19966020.

The previous prime is 19965997. The next prime is 19966027. The reversal of 19966021 is 12066991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11492100 + 8473921 = 3390^2 + 2911^2 .

It is a cyclic number.

It is not a de Polignac number, because 19966021 - 2⁹ = 19965509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19966027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9983010 + 9983011.

It is an arithmetic number, because the mean of its divisors is an integer number (9983011).

Almost surely, 2^19966021 is an apocalyptic number.

It is an amenable number.

19966021 is a deficient number, since it is larger than the sum of its proper divisors (1).

19966021 is an equidigital number, since it uses as much as digits as its factorization.

19966021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5832, while the sum is 34.

The square root of 19966021 is about 4468.3353723730. The cubic root of 19966021 is about 271.2879525282.

The spelling of 19966021 in words is "nineteen million, nine hundred sixty-six thousand, twenty-one".