21112517 has 4 divisors (see below), whose sum is σ = 21179436. Its totient is φ = 21045600.

The previous prime is 21112433. The next prime is 21112547. The reversal of 21112517 is 71521112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8145316 + 12967201 = 2854^2 + 3601^2 .

It is a cyclic number.

It is not a de Polignac number, because 21112517 - 2²⁴ = 4335301 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 (21112547) 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, 32984 + ... + 33617.

It is an arithmetic number, because the mean of its divisors is an integer number (5294859).

Almost surely, 2^21112517 is an apocalyptic number.

It is an amenable number.

21112517 is a deficient number, since it is larger than the sum of its proper divisors (66919).

21112517 is an equidigital number, since it uses as much as digits as its factorization.

21112517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66918.

The product of its digits is 140, while the sum is 20.

The square root of 21112517 is about 4594.8359056663. The cubic root of 21112517 is about 276.3842797021.

Adding to 21112517 its reverse (71521112), we get a palindrome (92633629).

The spelling of 21112517 in words is "twenty-one million, one hundred twelve thousand, five hundred seventeen".