21969439 has 4 divisors (see below), whose sum is σ = 22924656. Its totient is φ = 21014224.

The previous prime is 21969407. The next prime is 21969449. The reversal of 21969439 is 93496912.

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 21969439 - 2⁵ = 21969407 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21969395 and 21969404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21969449) 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, 477574 + ... + 477619.

It is an arithmetic number, because the mean of its divisors is an integer number (5731164).

Almost surely, 2^21969439 is an apocalyptic number.

21969439 is a deficient number, since it is larger than the sum of its proper divisors (955217).

21969439 is an equidigital number, since it uses as much as digits as its factorization.

21969439 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 955216.

The product of its digits is 104976, while the sum is 43.

The square root of 21969439 is about 4687.1568141038. The cubic root of 21969439 is about 280.0741257827.

The spelling of 21969439 in words is "twenty-one million, nine hundred sixty-nine thousand, four hundred thirty-nine".