19984721 has 2 divisors, whose sum is σ = 19984722. Its totient is φ = 19984720.

The previous prime is 19984717. The next prime is 19984747. The reversal of 19984721 is 12748991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13957696 + 6027025 = 3736^2 + 2455^2 .

It is a cyclic number.

It is not a de Polignac number, because 19984721 - 2² = 19984717 is a prime.

It is not a weakly prime, because it can be changed into another prime (19914721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9992360 + 9992361.

It is an arithmetic number, because the mean of its divisors is an integer number (9992361).

Almost surely, 2^19984721 is an apocalyptic number.

It is an amenable number.

19984721 is a deficient number, since it is larger than the sum of its proper divisors (1).

19984721 is an equidigital number, since it uses as much as digits as its factorization.

19984721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 41.

The square root of 19984721 is about 4470.4273844902. The cubic root of 19984721 is about 271.3726214053.

The spelling of 19984721 in words is "nineteen million, nine hundred eighty-four thousand, seven hundred twenty-one".