21728733 has 16 divisors (see below), whose sum is σ = 31374336. Its totient is φ = 13296960.

The previous prime is 21728719. The next prime is 21728741. The reversal of 21728733 is 33782712.

It is a de Polignac number, because none of the positive numbers 2^k-21728733 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21728694 and 21728703.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21728233) 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, 5991 + ... + 8907.

It is an arithmetic number, because the mean of its divisors is an integer number (1960896).

Almost surely, 2^21728733 is an apocalyptic number.

It is an amenable number.

21728733 is a deficient number, since it is larger than the sum of its proper divisors (9645603).

21728733 is a wasteful number, since it uses less digits than its factorization.

21728733 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3124.

The product of its digits is 14112, while the sum is 33.

The square root of 21728733 is about 4661.4089071868. The cubic root of 21728733 is about 279.0474990108.

The spelling of 21728733 in words is "twenty-one million, seven hundred twenty-eight thousand, seven hundred thirty-three".