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215681 is a prime number
BaseRepresentation
bin110100101010000001
3101221212012
4310222001
523400211
64342305
71555544
oct645201
9357765
10215681
11138054
12a4995
137722b
145885b
1543d8b
hex34a81

215681 has 2 divisors, whose sum is σ = 215682. Its totient is φ = 215680.

The previous prime is 215659. The next prime is 215687. The reversal of 215681 is 186512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 167281 + 48400 = 409^2 + 220^2 .

It is a cyclic number.

It is not a de Polignac number, because 215681 - 26 = 215617 is a prime.

It is a super-2 number, since 2×2156812 = 93036587522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (215687) 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, 107840 + 107841.

It is an arithmetic number, because the mean of its divisors is an integer number (107841).

2215681 is an apocalyptic number.

It is an amenable number.

215681 is a deficient number, since it is larger than the sum of its proper divisors (1).

215681 is an equidigital number, since it uses as much as digits as its factorization.

215681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 480, while the sum is 23.

The square root of 215681 is about 464.4146853837. The cubic root of 215681 is about 59.9704484104.

The spelling of 215681 in words is "two hundred fifteen thousand, six hundred eighty-one".