21231839 has 4 divisors (see below), whose sum is σ = 21316680. Its totient is φ = 21147000.

The previous prime is 21231823. The next prime is 21231841. The reversal of 21231839 is 93813212.

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 21231839 - 2⁴ = 21231823 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 (21231439) 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, 42044 + ... + 42545.

It is an arithmetic number, because the mean of its divisors is an integer number (5329170).

Almost surely, 2^21231839 is an apocalyptic number.

21231839 is a deficient number, since it is larger than the sum of its proper divisors (84841).

21231839 is an equidigital number, since it uses as much as digits as its factorization.

21231839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84840.

The product of its digits is 2592, while the sum is 29.

The square root of 21231839 is about 4607.8019705712. The cubic root of 21231839 is about 276.9039838906.

The spelling of 21231839 in words is "twenty-one million, two hundred thirty-one thousand, eight hundred thirty-nine".