21956423 has 2 divisors, whose sum is σ = 21956424. Its totient is φ = 21956422.

The previous prime is 21956399. The next prime is 21956461. The reversal of 21956423 is 32465912.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21956423 - 2¹⁰ = 21955399 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21956423.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21956323) 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, 10978211 + 10978212.

It is an arithmetic number, because the mean of its divisors is an integer number (10978212).

Almost surely, 2^21956423 is an apocalyptic number.

21956423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956423 is an equidigital number, since it uses as much as digits as its factorization.

21956423 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 32.

The square root of 21956423 is about 4685.7681334014. The cubic root of 21956423 is about 280.0188040093.

The spelling of 21956423 in words is "twenty-one million, nine hundred fifty-six thousand, four hundred twenty-three".