21129768 has 64 divisors (see below), whose sum is σ = 64036800. Its totient is φ = 6402240.

The previous prime is 21129761. The next prime is 21129781. The reversal of 21129768 is 86792112.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21129761) 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, 2071 + ... + 6822.

It is an arithmetic number, because the mean of its divisors is an integer number (1000575).

Almost surely, 2^21129768 is an apocalyptic number.

It is an amenable number.

21129768 is an abundant number, since it is smaller than the sum of its proper divisors (42907032).

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

21129768 is a wasteful number, since it uses less digits than its factorization.

21129768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8919 (or 8909 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21129768 is about 4596.7127384687. The cubic root of 21129768 is about 276.4595369090.

The spelling of 21129768 in words is "twenty-one million, one hundred twenty-nine thousand, seven hundred sixty-eight".