21682728 has 40 divisors (see below), whose sum is σ = 60733530. Its totient is φ = 7227360.

The previous prime is 21682709. The next prime is 21682757. The reversal of 21682728 is 82728612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18507204 + 3175524 = 4302^2 + 1782^2 .

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

It is a junction number, because it is equal to n+sod(n) for n = 21682692 and 21682701.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 16083 + ... + 17378.

Almost surely, 2^21682728 is an apocalyptic number.

It is an amenable number.

21682728 is an abundant number, since it is smaller than the sum of its proper divisors (39050802).

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

21682728 is a wasteful number, since it uses less digits than its factorization.

21682728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33479 (or 33466 counting only the distinct ones).

The product of its digits is 21504, while the sum is 36.

The square root of 21682728 is about 4656.4716255981. The cubic root of 21682728 is about 278.8504227714.

It can be divided in two parts, 216 and 82728, that added together give a square (82944 = 288²).

The spelling of 21682728 in words is "twenty-one million, six hundred eighty-two thousand, seven hundred twenty-eight".