21561117 has 16 divisors (see below), whose sum is σ = 30533760. Its totient is φ = 13486592.

The previous prime is 21561107. The next prime is 21561131. The reversal of 21561117 is 71116512.

It is a cyclic number.

It is not a de Polignac number, because 21561117 - 2⁴ = 21561101 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561107) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28648 + ... + 29390.

It is an arithmetic number, because the mean of its divisors is an integer number (1908360).

Almost surely, 2^21561117 is an apocalyptic number.

It is an amenable number.

21561117 is a deficient number, since it is larger than the sum of its proper divisors (8972643).

21561117 is a wasteful number, since it uses less digits than its factorization.

21561117 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1332.

The product of its digits is 420, while the sum is 24.

The square root of 21561117 is about 4643.3949864296. The cubic root of 21561117 is about 278.3281195513.

Adding to 21561117 its reverse (71116512), we get a palindrome (92677629).

The spelling of 21561117 in words is "twenty-one million, five hundred sixty-one thousand, one hundred seventeen".