21009612 has 24 divisors (see below), whose sum is σ = 52793776. Its totient is φ = 6464448.

The previous prime is 21009587. The next prime is 21009613. The reversal of 21009612 is 21690012.

It is not an unprimeable number, because it can be changed into a prime (21009613) 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, 67183 + ... + 67494.

Almost surely, 2^21009612 is an apocalyptic number.

It is an amenable number.

21009612 is an abundant number, since it is smaller than the sum of its proper divisors (31784164).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21009612 is a wasteful number, since it uses less digits than its factorization.

21009612 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134697 (or 134695 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 21.

The square root of 21009612 is about 4583.6243301562. The cubic root of 21009612 is about 275.9345045178.

Adding to 21009612 its reverse (21690012), we get a palindrome (42699624).

The spelling of 21009612 in words is "twenty-one million, nine thousand, six hundred twelve".