21381351 has 16 divisors (see below), whose sum is σ = 29644800. Its totient is φ = 13692960.

The previous prime is 21381317. The next prime is 21381361. The reversal of 21381351 is 15318312.

It is not a de Polignac number, because 21381351 - 2¹⁷ = 21250279 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381361) 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 15 ways as a sum of consecutive naturals, for example, 13086 + ... + 14628.

It is an arithmetic number, because the mean of its divisors is an integer number (1852800).

Almost surely, 2^21381351 is an apocalyptic number.

21381351 is a deficient number, since it is larger than the sum of its proper divisors (8263449).

21381351 is a wasteful number, since it uses less digits than its factorization.

21381351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1726.

The product of its digits is 720, while the sum is 24.

The square root of 21381351 is about 4623.9972967120. The cubic root of 21381351 is about 277.5524387550.

Adding to 21381351 its reverse (15318312), we get a palindrome (36699663).

The spelling of 21381351 in words is "twenty-one million, three hundred eighty-one thousand, three hundred fifty-one".