21097839 has 8 divisors (see below), whose sum is σ = 32149120. Its totient is φ = 12055896.

The previous prime is 21097823. The next prime is 21097841. The reversal of 21097839 is 93879012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21097839 - 2⁴ = 21097823 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21097797 and 21097806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21097859) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 502309 + ... + 502350.

It is an arithmetic number, because the mean of its divisors is an integer number (4018640).

Almost surely, 2^21097839 is an apocalyptic number.

21097839 is a deficient number, since it is larger than the sum of its proper divisors (11051281).

21097839 is a wasteful number, since it uses less digits than its factorization.

21097839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1004669.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21097839 is about 4593.2384000833. The cubic root of 21097839 is about 276.3202148798.

The spelling of 21097839 in words is "twenty-one million, ninety-seven thousand, eight hundred thirty-nine".