21946909 has 2 divisors, whose sum is σ = 21946910. Its totient is φ = 21946908.

The previous prime is 21946907. The next prime is 21946937. The reversal of 21946909 is 90964912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19316025 + 2630884 = 4395^2 + 1622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21946909 - 2¹ = 21946907 is a prime.

Together with 21946907, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21946907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10973454 + 10973455.

It is an arithmetic number, because the mean of its divisors is an integer number (10973455).

Almost surely, 2^21946909 is an apocalyptic number.

It is an amenable number.

21946909 is a deficient number, since it is larger than the sum of its proper divisors (1).

21946909 is an equidigital number, since it uses as much as digits as its factorization.

21946909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 34992, while the sum is 40.

The square root of 21946909 is about 4684.7528216545. The cubic root of 21946909 is about 279.9783529183.

The spelling of 21946909 in words is "twenty-one million, nine hundred forty-six thousand, nine hundred nine".