21217012 has 12 divisors (see below), whose sum is σ = 37638916. Its totient is φ = 10463040.

The previous prime is 21216997. The next prime is 21217019. The reversal of 21217012 is 21071212.

It can be written as a sum of positive squares in 2 ways, for example, as 5503716 + 15713296 = 2346^2 + 3964^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217019) 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, 36039 + ... + 36622.

Almost surely, 2^21217012 is an apocalyptic number.

It is an amenable number.

21217012 is a deficient number, since it is larger than the sum of its proper divisors (16421904).

21217012 is a wasteful number, since it uses less digits than its factorization.

21217012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72738 (or 72736 counting only the distinct ones).

The product of its (nonzero) digits is 56, while the sum is 16.

The square root of 21217012 is about 4606.1927879758. The cubic root of 21217012 is about 276.8395113555.

Adding to 21217012 its reverse (21071212), we get a palindrome (42288224).

The spelling of 21217012 in words is "twenty-one million, two hundred seventeen thousand, twelve".