21516839 has 4 divisors (see below), whose sum is σ = 21533520. Its totient is φ = 21500160.

The previous prime is 21516829. The next prime is 21516853. The reversal of 21516839 is 93861512.

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 21516839 - 2¹⁶ = 21451303 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21516799 and 21516808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21516829) 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, 6227 + ... + 9044.

It is an arithmetic number, because the mean of its divisors is an integer number (5383380).

Almost surely, 2^21516839 is an apocalyptic number.

21516839 is a deficient number, since it is larger than the sum of its proper divisors (16681).

21516839 is a wasteful number, since it uses less digits than its factorization.

21516839 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16680.

The product of its digits is 12960, while the sum is 35.

The square root of 21516839 is about 4638.6246884179. The cubic root of 21516839 is about 278.1374637178.

The spelling of 21516839 in words is "twenty-one million, five hundred sixteen thousand, eight hundred thirty-nine".