21728403 has 12 divisors (see below), whose sum is σ = 31448040. Its totient is φ = 14456736.

The previous prime is 21728393. The next prime is 21728407. The reversal of 21728403 is 30482712.

It is not a de Polignac number, because 21728403 - 2⁶ = 21728339 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21728407) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3000 + ... + 7242.

It is an arithmetic number, because the mean of its divisors is an integer number (2620670).

Almost surely, 2^21728403 is an apocalyptic number.

21728403 is a deficient number, since it is larger than the sum of its proper divisors (9719637).

21728403 is a wasteful number, since it uses less digits than its factorization.

21728403 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4818 (or 4815 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21728403 is about 4661.3735100290. The cubic root of 21728403 is about 279.0460863476.

The spelling of 21728403 in words is "twenty-one million, seven hundred twenty-eight thousand, four hundred three".