21761728 has 14 divisors (see below), whose sum is σ = 43183556. Its totient is φ = 10880832.

The previous prime is 21761723. The next prime is 21761731. The reversal of 21761728 is 82716712.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21761693 and 21761702.

It is not an unprimeable number, because it can be changed into a prime (21761723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 169950 + ... + 170077.

Almost surely, 2^21761728 is an apocalyptic number.

It is an amenable number.

21761728 is a deficient number, since it is larger than the sum of its proper divisors (21421828).

21761728 is an equidigital number, since it uses as much as digits as its factorization.

21761728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 340039 (or 340029 counting only the distinct ones).

The product of its digits is 9408, while the sum is 34.

The square root of 21761728 is about 4664.9467306712. The cubic root of 21761728 is about 279.1886717735.

The spelling of 21761728 in words is "twenty-one million, seven hundred sixty-one thousand, seven hundred twenty-eight".