21378329 has 4 divisors (see below), whose sum is σ = 24432384. Its totient is φ = 18324276.

The previous prime is 21378319. The next prime is 21378347. The reversal of 21378329 is 92387312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21378329 - 2¹² = 21374233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21378319) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1527017 + ... + 1527030.

It is an arithmetic number, because the mean of its divisors is an integer number (6108096).

Almost surely, 2^21378329 is an apocalyptic number.

It is an amenable number.

21378329 is a deficient number, since it is larger than the sum of its proper divisors (3054055).

21378329 is an equidigital number, since it uses as much as digits as its factorization.

21378329 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3054054.

The product of its digits is 18144, while the sum is 35.

The square root of 21378329 is about 4623.6705116174. The cubic root of 21378329 is about 277.5393618920.

The spelling of 21378329 in words is "twenty-one million, three hundred seventy-eight thousand, three hundred twenty-nine".