21954809 has 2 divisors, whose sum is σ = 21954810. Its totient is φ = 21954808.

The previous prime is 21954799. The next prime is 21954841. The reversal of 21954809 is 90845912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20502784 + 1452025 = 4528^2 + 1205^2 .

It is a cyclic number.

It is not a de Polignac number, because 21954809 - 2¹² = 21950713 is a prime.

It is not a weakly prime, because it can be changed into another prime (21954869) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10977404 + 10977405.

It is an arithmetic number, because the mean of its divisors is an integer number (10977405).

Almost surely, 2^21954809 is an apocalyptic number.

It is an amenable number.

21954809 is a deficient number, since it is larger than the sum of its proper divisors (1).

21954809 is an equidigital number, since it uses as much as digits as its factorization.

21954809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 21954809 is about 4685.5959066057. The cubic root of 21954809 is about 280.0119425178.

The spelling of 21954809 in words is "twenty-one million, nine hundred fifty-four thousand, eight hundred nine".