21388436 has 24 divisors (see below), whose sum is σ = 39541824. Its totient is φ = 10102400.

The previous prime is 21388421. The next prime is 21388439. The reversal of 21388436 is 63488312.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21388396 and 21388405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6236 + ... + 9036.

It is an arithmetic number, because the mean of its divisors is an integer number (1647576).

Almost surely, 2^21388436 is an apocalyptic number.

It is an amenable number.

21388436 is a deficient number, since it is larger than the sum of its proper divisors (18153388).

21388436 is a wasteful number, since it uses less digits than its factorization.

21388436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2911 (or 2909 counting only the distinct ones).

The product of its digits is 27648, while the sum is 35.

The square root of 21388436 is about 4624.7633452967. The cubic root of 21388436 is about 277.5830922883.

The spelling of 21388436 in words is "twenty-one million, three hundred eighty-eight thousand, four hundred thirty-six".