21393829 has 4 divisors (see below), whose sum is σ = 22519840. Its totient is φ = 20267820.

The previous prime is 21393809. The next prime is 21393847. The reversal of 21393829 is 92839312.

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 21393829 - 2¹⁷ = 21262757 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 (21393809) 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, 562977 + ... + 563014.

It is an arithmetic number, because the mean of its divisors is an integer number (5629960).

Almost surely, 2^21393829 is an apocalyptic number.

It is an amenable number.

21393829 is a deficient number, since it is larger than the sum of its proper divisors (1126011).

21393829 is a wasteful number, since it uses less digits than its factorization.

21393829 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1126010.

The product of its digits is 23328, while the sum is 37.

The square root of 21393829 is about 4625.3463654088. The cubic root of 21393829 is about 277.6064207793.

It can be divided in two parts, 21393 and 829, that added together give a palindrome (22222).

The spelling of 21393829 in words is "twenty-one million, three hundred ninety-three thousand, eight hundred twenty-nine".