21439009 has 4 divisors (see below), whose sum is σ = 21558960. Its totient is φ = 21319060.

The previous prime is 21438961. The next prime is 21439079. The reversal of 21439009 is 90093412.

It is a happy number.

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 21439009 - 2⁷ = 21438881 is a prime.

It is a super-2 number, since 2×21439009² = 919262213804162, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21439079) 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, 59707 + ... + 60064.

It is an arithmetic number, because the mean of its divisors is an integer number (5389740).

Almost surely, 2^21439009 is an apocalyptic number.

It is an amenable number.

21439009 is a deficient number, since it is larger than the sum of its proper divisors (119951).

21439009 is a wasteful number, since it uses less digits than its factorization.

21439009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119950.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 21439009 is about 4630.2277481783. The cubic root of 21439009 is about 277.8017020046.

The spelling of 21439009 in words is "twenty-one million, four hundred thirty-nine thousand, nine".