21112817 has 4 divisors (see below), whose sum is σ = 23032176. Its totient is φ = 19193460.

The previous prime is 21112813. The next prime is 21112831. The reversal of 21112817 is 71821112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21112817 - 2² = 21112813 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21112792 and 21112801.

It is not an unprimeable number, because it can be changed into a prime (21112813) 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, 959663 + ... + 959684.

It is an arithmetic number, because the mean of its divisors is an integer number (5758044).

Almost surely, 2^21112817 is an apocalyptic number.

It is an amenable number.

21112817 is a deficient number, since it is larger than the sum of its proper divisors (1919359).

21112817 is a wasteful number, since it uses less digits than its factorization.

21112817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1919358.

The product of its digits is 224, while the sum is 23.

The square root of 21112817 is about 4594.8685508946. The cubic root of 21112817 is about 276.3855887974.

Adding to 21112817 its reverse (71821112), we get a palindrome (92933929).

The spelling of 21112817 in words is "twenty-one million, one hundred twelve thousand, eight hundred seventeen".