21053909 has 2 divisors, whose sum is σ = 21053910. Its totient is φ = 21053908.

The previous prime is 21053897. The next prime is 21053941. The reversal of 21053909 is 90935012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 31684 = 4585^2 + 178^2 .

It is a cyclic number.

It is not a de Polignac number, because 21053909 - 2¹² = 21049813 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21053969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10526954 + 10526955.

It is an arithmetic number, because the mean of its divisors is an integer number (10526955).

Almost surely, 2^21053909 is an apocalyptic number.

It is an amenable number.

21053909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21053909 is an equidigital number, since it uses as much as digits as its factorization.

21053909 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2430, while the sum is 29.

The square root of 21053909 is about 4588.4538790316. The cubic root of 21053909 is about 276.1282966157.

The spelling of 21053909 in words is "twenty-one million, fifty-three thousand, nine hundred nine".