21009672 has 64 divisors (see below), whose sum is σ = 60912000. Its totient is φ = 6697152.

The previous prime is 21009643. The next prime is 21009679. The reversal of 21009672 is 27690012.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21009679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2854 + ... + 7082.

It is an arithmetic number, because the mean of its divisors is an integer number (951750).

Almost surely, 2^21009672 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21009672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30456000).

21009672 is an abundant number, since it is smaller than the sum of its proper divisors (39902328).

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

21009672 is a wasteful number, since it uses less digits than its factorization.

21009672 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4267 (or 4257 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21009672 is about 4583.6308751905. The cubic root of 21009672 is about 275.9347671921.

Adding to 21009672 its reverse (27690012), we get a palindrome (48699684).

The spelling of 21009672 in words is "twenty-one million, nine thousand, six hundred seventy-two".