21390288 has 20 divisors (see below), whose sum is σ = 55258368. Its totient is φ = 7130080.

The previous prime is 21390287. The next prime is 21390289. The reversal of 21390288 is 88209312.

It is an interprime number because it is at equal distance from previous prime (21390287) and next prime (21390289).

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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 222768 + ... + 222863.

Almost surely, 2^21390288 is an apocalyptic number.

It is an amenable number.

21390288 is an abundant number, since it is smaller than the sum of its proper divisors (33868080).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21390288 is a wasteful number, since it uses less digits than its factorization.

21390288 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 445642 (or 445636 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 21390288 is about 4624.9635674241. The cubic root of 21390288 is about 277.5911039236.

The spelling of 21390288 in words is "twenty-one million, three hundred ninety thousand, two hundred eighty-eight".