21645339 has 8 divisors (see below), whose sum is σ = 29855760. Its totient is φ = 13932576.

The previous prime is 21645331. The next prime is 21645343. The reversal of 21645339 is 93354612.

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

It is not a de Polignac number, because 21645339 - 2³ = 21645331 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21645331) 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, 124312 + ... + 124485.

It is an arithmetic number, because the mean of its divisors is an integer number (3731970).

Almost surely, 2^21645339 is an apocalyptic number.

21645339 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21645339 is a deficient number, since it is larger than the sum of its proper divisors (8210421).

21645339 is a wasteful number, since it uses less digits than its factorization.

21645339 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248829.

The product of its digits is 19440, while the sum is 33.

The square root of 21645339 is about 4652.4551583008. The cubic root of 21645339 is about 278.6900503170.

It can be divided in two parts, 2164 and 5339, that added together give a triangular number (7503 = T₁₂₂).

The spelling of 21645339 in words is "twenty-one million, six hundred forty-five thousand, three hundred thirty-nine".