21390286 has 8 divisors (see below), whose sum is σ = 32564520. Its totient is φ = 10535448.

The previous prime is 21390283. The next prime is 21390287. The reversal of 21390286 is 68209312.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390283) 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 3 ways as a sum of consecutive naturals, for example, 79681 + ... + 79948.

It is an arithmetic number, because the mean of its divisors is an integer number (4070565).

Almost surely, 2^21390286 is an apocalyptic number.

21390286 is a deficient number, since it is larger than the sum of its proper divisors (11174234).

21390286 is a wasteful number, since it uses less digits than its factorization.

21390286 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159698.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21390286 is about 4624.9633512061. The cubic root of 21390286 is about 277.5910952720.

Adding to 21390286 its reverse (68209312), we get a palindrome (89599598).

The spelling of 21390286 in words is "twenty-one million, three hundred ninety thousand, two hundred eighty-six".