21145109 has 2 divisors, whose sum is σ = 21145110. Its totient is φ = 21145108.

The previous prime is 21145079. The next prime is 21145141. The reversal of 21145109 is 90154112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20295025 + 850084 = 4505^2 + 922^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21145109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21145169) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10572554 + 10572555.

It is an arithmetic number, because the mean of its divisors is an integer number (10572555).

Almost surely, 2^21145109 is an apocalyptic number.

It is an amenable number.

21145109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21145109 is an equidigital number, since it uses as much as digits as its factorization.

21145109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 23.

The square root of 21145109 is about 4598.3811281798. The cubic root of 21145109 is about 276.5264273698.

The spelling of 21145109 in words is "twenty-one million, one hundred forty-five thousand, one hundred nine".