21904643 has 2 divisors, whose sum is σ = 21904644. Its totient is φ = 21904642.

The previous prime is 21904609. The next prime is 21904691. The reversal of 21904643 is 34640912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21904643 - 2¹⁴ = 21888259 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21904343) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10952321 + 10952322.

It is an arithmetic number, because the mean of its divisors is an integer number (10952322).

Almost surely, 2^21904643 is an apocalyptic number.

21904643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21904643 is an equidigital number, since it uses as much as digits as its factorization.

21904643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 21904643 is about 4680.2396306172. The cubic root of 21904643 is about 279.7985072481.

The spelling of 21904643 in words is "twenty-one million, nine hundred four thousand, six hundred forty-three".