19638821 has 2 divisors, whose sum is σ = 19638822. Its totient is φ = 19638820.

The previous prime is 19638797. The next prime is 19638833. The reversal of 19638821 is 12883691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17430625 + 2208196 = 4175^2 + 1486^2 .

It is a cyclic number.

It is not a de Polignac number, because 19638821 - 2¹⁰ = 19637797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19638121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9819410 + 9819411.

It is an arithmetic number, because the mean of its divisors is an integer number (9819411).

Almost surely, 2^19638821 is an apocalyptic number.

It is an amenable number.

19638821 is a deficient number, since it is larger than the sum of its proper divisors (1).

19638821 is an equidigital number, since it uses as much as digits as its factorization.

19638821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 38.

The square root of 19638821 is about 4431.5709404228. The cubic root of 19638821 is about 269.7978413584.

The spelling of 19638821 in words is "nineteen million, six hundred thirty-eight thousand, eight hundred twenty-one".