21378313 has 16 divisors (see below), whose sum is σ = 24440832. Its totient is φ = 18522000.

The previous prime is 21378289. The next prime is 21378317. The reversal of 21378313 is 31387312.

It is a cyclic number.

It is not a de Polignac number, because 21378313 - 2⁵ = 21378281 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21378317) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 23770 + ... + 24652.

It is an arithmetic number, because the mean of its divisors is an integer number (1527552).

Almost surely, 2^21378313 is an apocalyptic number.

It is an amenable number.

21378313 is a deficient number, since it is larger than the sum of its proper divisors (3062519).

21378313 is a wasteful number, since it uses less digits than its factorization.

21378313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 996.

The product of its digits is 3024, while the sum is 28.

The square root of 21378313 is about 4623.6687813899. The cubic root of 21378313 is about 277.5392926532.

The spelling of 21378313 in words is "twenty-one million, three hundred seventy-eight thousand, three hundred thirteen".