21007668 has 48 divisors (see below), whose sum is σ = 54371520. Its totient is φ = 6259200.

The previous prime is 21007639. The next prime is 21007669. The reversal of 21007668 is 86670012.

It is a happy number.

It is a super-2 number, since 2×21007668² = 882644229596448, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21007669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6748 + ... + 9356.

It is an arithmetic number, because the mean of its divisors is an integer number (1132740).

Almost surely, 2^21007668 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 21007668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27185760).

21007668 is an abundant number, since it is smaller than the sum of its proper divisors (33363852).

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

21007668 is a wasteful number, since it uses less digits than its factorization.

21007668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2688 (or 2686 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 30.

The square root of 21007668 is about 4583.4122659870. The cubic root of 21007668 is about 275.9259936003.

The spelling of 21007668 in words is "twenty-one million, seven thousand, six hundred sixty-eight".