19613921 has 2 divisors, whose sum is σ = 19613922. Its totient is φ = 19613920.

The previous prime is 19613887. The next prime is 19613929. The reversal of 19613921 is 12931691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15713296 + 3900625 = 3964^2 + 1975^2 .

It is a cyclic number.

It is not a de Polignac number, because 19613921 - 2¹⁴ = 19597537 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (19613929) 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, 9806960 + 9806961.

It is an arithmetic number, because the mean of its divisors is an integer number (9806961).

Almost surely, 2^19613921 is an apocalyptic number.

It is an amenable number.

19613921 is a deficient number, since it is larger than the sum of its proper divisors (1).

19613921 is an equidigital number, since it uses as much as digits as its factorization.

19613921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2916, while the sum is 32.

The square root of 19613921 is about 4428.7606618556. The cubic root of 19613921 is about 269.6837678527.

It can be divided in two parts, 1961 and 3921, that multiplied together give a triangular number (7689081 = T₃₉₂₁).

The spelling of 19613921 in words is "nineteen million, six hundred thirteen thousand, nine hundred twenty-one".