21147 has 16 divisors (see below), whose sum is σ = 34560. Its totient is φ = 11232.

The previous prime is 21143. The next prime is 21149. The reversal of 21147 is 74112.

Adding to 21147 its reverse (74112), we get a palindrome (95259).

It is the 9-th Bell number.

It is not a de Polignac number, because 21147 - 2^{2} = 21143 is a prime.

21147 is a lucky number.

It is an inconsummate number, since it does not exist a number *n* which divided by its sum of digits gives 21147.

It is not an unprimeable number, because it can be changed into a prime (21143) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 373 + ... + 425.

It is an arithmetic number, because the mean of its divisors is an integer number (2160).

2^{21147} is an apocalyptic number.

21147 is a deficient number, since it is larger than the sum of its proper divisors (13413).

21147 is a wasteful number, since it uses less digits than its factorization.

21147 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82.

The product of its digits is 56, while the sum is 15.

The square root of 21147 is about 145.4200811442. The cubic root of 21147 is about 27.6534670346.

The spelling of 21147 in words is "twenty-one thousand, one hundred forty-seven", and thus it is an iban number.

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