21173839 has 4 divisors (see below), whose sum is σ = 21392224. Its totient is φ = 20955456.

The previous prime is 21173807. The next prime is 21173849. The reversal of 21173839 is 93837112.

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 21173839 - 2⁵ = 21173807 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 (21173849) 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, 109047 + ... + 109240.

It is an arithmetic number, because the mean of its divisors is an integer number (5348056).

Almost surely, 2^21173839 is an apocalyptic number.

21173839 is a deficient number, since it is larger than the sum of its proper divisors (218385).

21173839 is an equidigital number, since it uses as much as digits as its factorization.

21173839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 218384.

The product of its digits is 9072, while the sum is 34.

The square root of 21173839 is about 4601.5039932613. The cubic root of 21173839 is about 276.6516101224.

The spelling of 21173839 in words is "twenty-one million, one hundred seventy-three thousand, eight hundred thirty-nine".