21016388 has 24 divisors (see below), whose sum is σ = 39621120. Its totient is φ = 9725760.

The previous prime is 21016381. The next prime is 21016393. The reversal of 21016388 is 88361012.

It is a self number, because there is not a number n which added to its sum of digits gives 21016388.

It is not an unprimeable number, because it can be changed into a prime (21016381) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 833 + ... + 6536.

It is an arithmetic number, because the mean of its divisors is an integer number (1650880).

Almost surely, 2^21016388 is an apocalyptic number.

It is an amenable number.

21016388 is a deficient number, since it is larger than the sum of its proper divisors (18604732).

21016388 is a wasteful number, since it uses less digits than its factorization.

21016388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7427 (or 7425 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21016388 is about 4584.3634236391. The cubic root of 21016388 is about 275.9641660402.

The spelling of 21016388 in words is "twenty-one million, sixteen thousand, three hundred eighty-eight".