21345439 has 4 divisors (see below), whose sum is σ = 21473424. Its totient is φ = 21217456.

The previous prime is 21345431. The next prime is 21345451. The reversal of 21345439 is 93454312.

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 21345439 - 2³ = 21345431 is a prime.

It is a super-2 number, since 2×21345439² = 911255532205442, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21345439.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21345431) 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, 63742 + ... + 64075.

It is an arithmetic number, because the mean of its divisors is an integer number (5368356).

Almost surely, 2^21345439 is an apocalyptic number.

21345439 is a deficient number, since it is larger than the sum of its proper divisors (127985).

21345439 is a wasteful number, since it uses less digits than its factorization.

21345439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127984.

The product of its digits is 12960, while the sum is 31.

The square root of 21345439 is about 4620.1124445191. The cubic root of 21345439 is about 277.3969598234.

The spelling of 21345439 in words is "twenty-one million, three hundred forty-five thousand, four hundred thirty-nine".