21287351 has 8 divisors (see below), whose sum is σ = 22272000. Its totient is φ = 20307672.

The previous prime is 21287347. The next prime is 21287389. The reversal of 21287351 is 15378212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21287351 - 2² = 21287347 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9650 + ... + 11648.

It is an arithmetic number, because the mean of its divisors is an integer number (2784000).

Almost surely, 2^21287351 is an apocalyptic number.

21287351 is a deficient number, since it is larger than the sum of its proper divisors (984649).

21287351 is a wasteful number, since it uses less digits than its factorization.

21287351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2485.

The product of its digits is 3360, while the sum is 29.

The square root of 21287351 is about 4613.8217347444. The cubic root of 21287351 is about 277.1451015943.

The spelling of 21287351 in words is "twenty-one million, two hundred eighty-seven thousand, three hundred fifty-one".