21438911 has 4 divisors (see below), whose sum is σ = 23088072. Its totient is φ = 19789752.

The previous prime is 21438881. The next prime is 21438913. The reversal of 21438911 is 11983412.

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 21438911 - 2⁶ = 21438847 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21438913) 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, 824561 + ... + 824586.

It is an arithmetic number, because the mean of its divisors is an integer number (5772018).

Almost surely, 2^21438911 is an apocalyptic number.

21438911 is a deficient number, since it is larger than the sum of its proper divisors (1649161).

21438911 is a wasteful number, since it uses less digits than its factorization.

21438911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1649160.

The product of its digits is 1728, while the sum is 29.

The square root of 21438911 is about 4630.2171655334. The cubic root of 21438911 is about 277.8012787169.

The spelling of 21438911 in words is "twenty-one million, four hundred thirty-eight thousand, nine hundred eleven".