19986121 has 2 divisors, whose sum is σ = 19986122. Its totient is φ = 19986120.

The previous prime is 19986091. The next prime is 19986137. The reversal of 19986121 is 12168991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19678096 + 308025 = 4436^2 + 555^2 .

It is a cyclic number.

It is not a de Polignac number, because 19986121 - 2¹¹ = 19984073 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19996121) 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, 9993060 + 9993061.

It is an arithmetic number, because the mean of its divisors is an integer number (9993061).

Almost surely, 2^19986121 is an apocalyptic number.

It is an amenable number.

19986121 is a deficient number, since it is larger than the sum of its proper divisors (1).

19986121 is an equidigital number, since it uses as much as digits as its factorization.

19986121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776, while the sum is 37.

The square root of 19986121 is about 4470.5839663292. The cubic root of 19986121 is about 271.3789581262.

It can be divided in two parts, 199 and 86121, that added together give a triangular number (86320 = T₄₁₅).

The spelling of 19986121 in words is "nineteen million, nine hundred eighty-six thousand, one hundred twenty-one".