21439207 has 4 divisors (see below), whose sum is σ = 22178520. Its totient is φ = 20699896.

The previous prime is 21439199. The next prime is 21439211. The reversal of 21439207 is 70293412.

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 21439207 - 2³ = 21439199 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 (21439217) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 369613 + ... + 369670.

It is an arithmetic number, because the mean of its divisors is an integer number (5544630).

Almost surely, 2^21439207 is an apocalyptic number.

21439207 is a deficient number, since it is larger than the sum of its proper divisors (739313).

21439207 is an equidigital number, since it uses as much as digits as its factorization.

21439207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 739312.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21439207 is about 4630.2491293666. The cubic root of 21439207 is about 277.8025572146.

The spelling of 21439207 in words is "twenty-one million, four hundred thirty-nine thousand, two hundred seven".