21217316 has 24 divisors (see below), whose sum is σ = 38963904. Its totient is φ = 10090080.

The previous prime is 21217307. The next prime is 21217337. The reversal of 21217316 is 61371212.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a junction number, because it is equal to n+sod(n) for n = 21217291 and 21217300.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18866 + ... + 19958.

It is an arithmetic number, because the mean of its divisors is an integer number (1623496).

Almost surely, 2^21217316 is an apocalyptic number.

It is an amenable number.

21217316 is a deficient number, since it is larger than the sum of its proper divisors (17746588).

21217316 is a wasteful number, since it uses less digits than its factorization.

21217316 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1331 (or 1329 counting only the distinct ones).

The product of its digits is 504, while the sum is 23.

The square root of 21217316 is about 4606.2257869106. The cubic root of 21217316 is about 276.8408335463.

Adding to 21217316 its reverse (61371212), we get a palindrome (82588528).

The spelling of 21217316 in words is "twenty-one million, two hundred seventeen thousand, three hundred sixteen".