21000388 has 12 divisors (see below), whose sum is σ = 36788220. Its totient is φ = 10489472.

The previous prime is 21000367. The next prime is 21000391. The reversal of 21000388 is 88300012.

It can be written as a sum of positive squares in 2 ways, for example, as 9290304 + 11710084 = 3048^2 + 3422^2 .

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, 3120 + ... + 7192.

It is an arithmetic number, because the mean of its divisors is an integer number (3065685).

Almost surely, 2^21000388 is an apocalyptic number.

It is an amenable number.

21000388 is a deficient number, since it is larger than the sum of its proper divisors (15787832).

21000388 is a wasteful number, since it uses less digits than its factorization.

21000388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5366 (or 5364 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 22.

The square root of 21000388 is about 4582.6180290310. The cubic root of 21000388 is about 275.8941167746.

The spelling of 21000388 in words is "twenty-one million, three hundred eighty-eight", and thus it is an aban number.