21321388 has 12 divisors (see below), whose sum is σ = 40704552. Its totient is φ = 9691520.

The previous prime is 21321379. The next prime is 21321407. The reversal of 21321388 is 88312312.

It is a plaindrome in base 16.

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, 242245 + ... + 242332.

It is an arithmetic number, because the mean of its divisors is an integer number (3392046).

Almost surely, 2^21321388 is an apocalyptic number.

It is an amenable number.

21321388 is a deficient number, since it is larger than the sum of its proper divisors (19383164).

21321388 is a wasteful number, since it uses less digits than its factorization.

21321388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 484592 (or 484590 counting only the distinct ones).

The product of its digits is 2304, while the sum is 28.

The square root of 21321388 is about 4617.5088521843. The cubic root of 21321388 is about 277.2927348783.

The spelling of 21321388 in words is "twenty-one million, three hundred twenty-one thousand, three hundred eighty-eight".