21154709 has 2 divisors, whose sum is σ = 21154710. Its totient is φ = 21154708.

The previous prime is 21154673. The next prime is 21154711. The reversal of 21154709 is 90745112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17556100 + 3598609 = 4190^2 + 1897^2 .

It is a cyclic number.

It is not a de Polignac number, because 21154709 - 2²⁴ = 4377493 is a prime.

It is a Sophie Germain prime.

Together with 21154711, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21154759) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577354 + 10577355.

It is an arithmetic number, because the mean of its divisors is an integer number (10577355).

Almost surely, 2^21154709 is an apocalyptic number.

It is an amenable number.

21154709 is a deficient number, since it is larger than the sum of its proper divisors (1).

21154709 is an equidigital number, since it uses as much as digits as its factorization.

21154709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 21154709 is about 4599.4248553488. The cubic root of 21154709 is about 276.5682692297.

The spelling of 21154709 in words is "twenty-one million, one hundred fifty-four thousand, seven hundred nine".