21511109 has 2 divisors, whose sum is σ = 21511110. Its totient is φ = 21511108.

The previous prime is 21511093. The next prime is 21511151. The reversal of 21511109 is 90111512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21362884 + 148225 = 4622^2 + 385^2 .

It is a cyclic number.

It is not a de Polignac number, because 21511109 - 2⁴ = 21511093 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 (21511159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755554 + 10755555.

It is an arithmetic number, because the mean of its divisors is an integer number (10755555).

Almost surely, 2^21511109 is an apocalyptic number.

It is an amenable number.

21511109 is a deficient number, since it is larger than the sum of its proper divisors (1).

21511109 is an equidigital number, since it uses as much as digits as its factorization.

21511109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90, while the sum is 20.

The square root of 21511109 is about 4638.0070073255. The cubic root of 21511109 is about 278.1127719069.

The spelling of 21511109 in words is "twenty-one million, five hundred eleven thousand, one hundred nine".