19739821 has 2 divisors, whose sum is σ = 19739822. Its totient is φ = 19739820.

The previous prime is 19739813. The next prime is 19739827. The reversal of 19739821 is 12893791.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19624900 + 114921 = 4430^2 + 339^2 .

It is an emirp because it is prime and its reverse (12893791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19739821 - 2³ = 19739813 is a prime.

It is a super-2 number, since 2×19739821² = 779321066224082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19739827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9869910 + 9869911.

It is an arithmetic number, because the mean of its divisors is an integer number (9869911).

Almost surely, 2^19739821 is an apocalyptic number.

It is an amenable number.

19739821 is a deficient number, since it is larger than the sum of its proper divisors (1).

19739821 is an equidigital number, since it uses as much as digits as its factorization.

19739821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 40.

The square root of 19739821 is about 4442.9518340851. The cubic root of 19739821 is about 270.2595629193.

The spelling of 19739821 in words is "nineteen million, seven hundred thirty-nine thousand, eight hundred twenty-one".