21338921 has 4 divisors (see below), whose sum is σ = 21507072. Its totient is φ = 21170772.

The previous prime is 21338873. The next prime is 21338929. The reversal of 21338921 is 12983312.

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 21338921 - 2⁶ = 21338857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21338929) 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, 83885 + ... + 84138.

It is an arithmetic number, because the mean of its divisors is an integer number (5376768).

Almost surely, 2^21338921 is an apocalyptic number.

It is an amenable number.

21338921 is a deficient number, since it is larger than the sum of its proper divisors (168151).

21338921 is a wasteful number, since it uses less digits than its factorization.

21338921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168150.

The product of its digits is 2592, while the sum is 29.

The square root of 21338921 is about 4619.4069965743. The cubic root of 21338921 is about 277.3687218245.

The spelling of 21338921 in words is "twenty-one million, three hundred thirty-eight thousand, nine hundred twenty-one".