21381323 has 4 divisors (see below), whose sum is σ = 22118640. Its totient is φ = 20644008.

The previous prime is 21381317. The next prime is 21381361. The reversal of 21381323 is 32318312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21381323 - 2⁴ = 21381307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21381383) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 368615 + ... + 368672.

It is an arithmetic number, because the mean of its divisors is an integer number (5529660).

Almost surely, 2^21381323 is an apocalyptic number.

21381323 is a deficient number, since it is larger than the sum of its proper divisors (737317).

21381323 is an equidigital number, since it uses as much as digits as its factorization.

21381323 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 737316.

The product of its digits is 864, while the sum is 23.

The square root of 21381323 is about 4623.9942690276. The cubic root of 21381323 is about 277.5523175984.

Adding to 21381323 its reverse (32318312), we get a palindrome (53699635).

The spelling of 21381323 in words is "twenty-one million, three hundred eighty-one thousand, three hundred twenty-three".