21728316 has 12 divisors (see below), whose sum is σ = 50699432. Its totient is φ = 7242768.

The previous prime is 21728309. The next prime is 21728323. The reversal of 21728316 is 61382712.

It is an interprime number because it is at equal distance from previous prime (21728309) and next prime (21728323).

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 905335 + ... + 905358.

Almost surely, 2^21728316 is an apocalyptic number.

It is an amenable number.

21728316 is an abundant number, since it is smaller than the sum of its proper divisors (28971116).

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

21728316 is a wasteful number, since it uses less digits than its factorization.

21728316 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1810700 (or 1810698 counting only the distinct ones).

The product of its digits is 4032, while the sum is 30.

The square root of 21728316 is about 4661.3641780063. The cubic root of 21728316 is about 279.0457139159.

The spelling of 21728316 in words is "twenty-one million, seven hundred twenty-eight thousand, three hundred sixteen".