21408319 has 2 divisors, whose sum is σ = 21408320. Its totient is φ = 21408318.

The previous prime is 21408301. The next prime is 21408329. The reversal of 21408319 is 91380412.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21408319 - 2¹¹ = 21406271 is a prime.

It is a super-3 number, since 3×21408319³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21408329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10704159 + 10704160.

It is an arithmetic number, because the mean of its divisors is an integer number (10704160).

Almost surely, 2^21408319 is an apocalyptic number.

21408319 is a deficient number, since it is larger than the sum of its proper divisors (1).

21408319 is an equidigital number, since it uses as much as digits as its factorization.

21408319 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21408319 is about 4626.9124694552. The cubic root of 21408319 is about 277.6690807366.

The spelling of 21408319 in words is "twenty-one million, four hundred eight thousand, three hundred nineteen".