21442009 has 2 divisors, whose sum is σ = 21442010. Its totient is φ = 21442008.

The previous prime is 21441989. The next prime is 21442019. The reversal of 21442009 is 90024412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20385225 + 1056784 = 4515^2 + 1028^2 .

It is a cyclic number.

It is not a de Polignac number, because 21442009 - 2⁷ = 21441881 is a prime.

It is not a weakly prime, because it can be changed into another prime (21442019) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10721004 + 10721005.

It is an arithmetic number, because the mean of its divisors is an integer number (10721005).

Almost surely, 2^21442009 is an apocalyptic number.

It is an amenable number.

21442009 is a deficient number, since it is larger than the sum of its proper divisors (1).

21442009 is an equidigital number, since it uses as much as digits as its factorization.

21442009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21442009 is about 4630.5516949927. The cubic root of 21442009 is about 277.8146591681.

The spelling of 21442009 in words is "twenty-one million, four hundred forty-two thousand, nine".