21819643 has 2 divisors, whose sum is σ = 21819644. Its totient is φ = 21819642.

The previous prime is 21819601. The next prime is 21819647. The reversal of 21819643 is 34691812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21819643 - 2¹⁷ = 21688571 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21819599 and 21819608.

It is not a weakly prime, because it can be changed into another prime (21819647) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909821 + 10909822.

It is an arithmetic number, because the mean of its divisors is an integer number (10909822).

Almost surely, 2^21819643 is an apocalyptic number.

21819643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21819643 is an equidigital number, since it uses as much as digits as its factorization.

21819643 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 34.

The square root of 21819643 is about 4671.1500725196. The cubic root of 21819643 is about 279.4361228531.

The spelling of 21819643 in words is "twenty-one million, eight hundred nineteen thousand, six hundred forty-three".