21213117 has 8 divisors (see below), whose sum is σ = 31426880. Its totient is φ = 14142060.

The previous prime is 21213109. The next prime is 21213119. The reversal of 21213117 is 71131212.

It is a happy number.

It is not a de Polignac number, because 21213117 - 2³ = 21213109 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21213117.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213119) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 392809 + ... + 392862.

It is an arithmetic number, because the mean of its divisors is an integer number (3928360).

Almost surely, 2^21213117 is an apocalyptic number.

21213117 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21213117 is a deficient number, since it is larger than the sum of its proper divisors (10213763).

21213117 is an equidigital number, since it uses as much as digits as its factorization.

21213117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 785680 (or 785674 counting only the distinct ones).

The product of its digits is 84, while the sum is 18.

The square root of 21213117 is about 4605.7699682029. The cubic root of 21213117 is about 276.8225696692.

Adding to 21213117 its reverse (71131212), we get a palindrome (92344329).

The spelling of 21213117 in words is "twenty-one million, two hundred thirteen thousand, one hundred seventeen".