21909101 has 2 divisors, whose sum is σ = 21909102. Its totient is φ = 21909100.

The previous prime is 21909089. The next prime is 21909103. The reversal of 21909101 is 10190912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14478025 + 7431076 = 3805^2 + 2726^2 .

It is a cyclic number.

It is not a de Polignac number, because 21909101 - 2¹⁰ = 21908077 is a prime.

Together with 21909103, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21909103) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10954550 + 10954551.

It is an arithmetic number, because the mean of its divisors is an integer number (10954551).

Almost surely, 2^21909101 is an apocalyptic number.

It is an amenable number.

21909101 is a deficient number, since it is larger than the sum of its proper divisors (1).

21909101 is an equidigital number, since it uses as much as digits as its factorization.

21909101 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 162, while the sum is 23.

The square root of 21909101 is about 4680.7158640533. The cubic root of 21909101 is about 279.8174873510.

The spelling of 21909101 in words is "twenty-one million, nine hundred nine thousand, one hundred one".