21967409 has 2 divisors, whose sum is σ = 21967410. Its totient is φ = 21967408.

The previous prime is 21967403. The next prime is 21967433. The reversal of 21967409 is 90476912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11424400 + 10543009 = 3380^2 + 3247^2 .

It is a cyclic number.

It is not a de Polignac number, because 21967409 - 2¹² = 21963313 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21967403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10983704 + 10983705.

It is an arithmetic number, because the mean of its divisors is an integer number (10983705).

Almost surely, 2^21967409 is an apocalyptic number.

It is an amenable number.

21967409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21967409 is an equidigital number, since it uses as much as digits as its factorization.

21967409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 21967409 is about 4686.9402599137. The cubic root of 21967409 is about 280.0654991327.

The spelling of 21967409 in words is "twenty-one million, nine hundred sixty-seven thousand, four hundred nine".