21116605 has 8 divisors (see below), whose sum is σ = 25364952. Its totient is φ = 16876608.

The previous prime is 21116597. The next prime is 21116629. The reversal of 21116605 is 50661112.

It can be written as a sum of positive squares in 4 ways, for example, as 6046681 + 15069924 = 2459^2 + 3882^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21116605 - 2³ = 21116597 is a prime.

It is a super-2 number, since 2×21116605² = 891822013452050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7447 + ... + 9883.

It is an arithmetic number, because the mean of its divisors is an integer number (3170619).

Almost surely, 2^21116605 is an apocalyptic number.

It is an amenable number.

21116605 is a deficient number, since it is larger than the sum of its proper divisors (4248347).

21116605 is a wasteful number, since it uses less digits than its factorization.

21116605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4175.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 21116605 is about 4595.2807313591. The cubic root of 21116605 is about 276.4021172408.

Adding to 21116605 its reverse (50661112), we get a palindrome (71777717).

The spelling of 21116605 in words is "twenty-one million, one hundred sixteen thousand, six hundred five".