21037728 has 24 divisors (see below), whose sum is σ = 55224288. Its totient is φ = 7012544.

The previous prime is 21037727. The next prime is 21037729. The reversal of 21037728 is 82773012.

It is an interprime number because it is at equal distance from previous prime (21037727) and next prime (21037729).

It is a tau number, because it is divible by the number of its divisors (24).

It is a junction number, because it is equal to n+sod(n) for n = 21037695 and 21037704.

It is not an unprimeable number, because it can be changed into a prime (21037727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109476 + ... + 109667.

It is an arithmetic number, because the mean of its divisors is an integer number (2301012).

Almost surely, 2^21037728 is an apocalyptic number.

It is an amenable number.

21037728 is an abundant number, since it is smaller than the sum of its proper divisors (34186560).

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

21037728 is a wasteful number, since it uses less digits than its factorization.

21037728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219156 (or 219148 counting only the distinct ones).

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 21037728 is about 4586.6903100166. The cubic root of 21037728 is about 276.0575389384.

The spelling of 21037728 in words is "twenty-one million, thirty-seven thousand, seven hundred twenty-eight".