21388 has 6 divisors (see below), whose sum is σ = 37436. Its totient is φ = 10692.
The previous prime is 21383. The next prime is 21391. The reversal of 21388 is 88312.
It is a nialpdrome in base 13.
It is not an unprimeable number, because it can be changed into a prime (21383) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2670 + ... + 2677.
221388 is an apocalyptic number.
It is an amenable number.
21388 is a deficient number, since it is larger than the sum of its proper divisors (16048).
21388 is a wasteful number, since it uses less digits than its factorization.
21388 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 5351 (or 5349 counting only the distinct ones).
The product of its digits is 384, while the sum is 22.
The square root of 21388 is about 146.2463674763. The cubic root of 21388 is about 27.7581206112.
The spelling of 21388 in words is "twenty-one thousand, three hundred eighty-eight".
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