21388347 has 24 divisors (see below), whose sum is σ = 32694480. Its totient is φ = 13811040.

The previous prime is 21388333. The next prime is 21388373. The reversal of 21388347 is 74388312.

It is not a de Polignac number, because 21388347 - 2⁷ = 21388219 is a prime.

It is a super-2 number, since 2×21388347² = 914922774784818, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21388327) 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 23 ways as a sum of consecutive naturals, for example, 153804 + ... + 153942.

It is an arithmetic number, because the mean of its divisors is an integer number (1362270).

Almost surely, 2^21388347 is an apocalyptic number.

21388347 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21388347 is a deficient number, since it is larger than the sum of its proper divisors (11306133).

21388347 is an equidigital number, since it uses as much as digits as its factorization.

21388347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 183 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 21388347 is about 4624.7537231727. The cubic root of 21388347 is about 277.5827072682.

The spelling of 21388347 in words is "twenty-one million, three hundred eighty-eight thousand, three hundred forty-seven".