21189439 has 4 divisors (see below), whose sum is σ = 21331800. Its totient is φ = 21047080.

The previous prime is 21189431. The next prime is 21189449. The reversal of 21189439 is 93498112.

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 21189439 - 2³ = 21189431 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21189398 and 21189407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21189431) 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, 70957 + ... + 71254.

It is an arithmetic number, because the mean of its divisors is an integer number (5332950).

Almost surely, 2^21189439 is an apocalyptic number.

21189439 is a deficient number, since it is larger than the sum of its proper divisors (142361).

21189439 is a wasteful number, since it uses less digits than its factorization.

21189439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142360.

The product of its digits is 15552, while the sum is 37.

The square root of 21189439 is about 4603.1987791100. The cubic root of 21189439 is about 276.7195352266.

The spelling of 21189439 in words is "twenty-one million, one hundred eighty-nine thousand, four hundred thirty-nine".