19723421 has 2 divisors, whose sum is σ = 19723422. Its totient is φ = 19723420.

The previous prime is 19723411. The next prime is 19723433. The reversal of 19723421 is 12432791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17131321 + 2592100 = 4139^2 + 1610^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19723421 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19723411) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9861710 + 9861711.

It is an arithmetic number, because the mean of its divisors is an integer number (9861711).

Almost surely, 2^19723421 is an apocalyptic number.

It is an amenable number.

19723421 is a deficient number, since it is larger than the sum of its proper divisors (1).

19723421 is an equidigital number, since it uses as much as digits as its factorization.

19723421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 29.

The square root of 19723421 is about 4441.1058307588. The cubic root of 19723421 is about 270.1846975858.

The spelling of 19723421 in words is "nineteen million, seven hundred twenty-three thousand, four hundred twenty-one".