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18821921 is a prime number
BaseRepresentation
bin100011111001…
…1001100100001
31022102020211012
41013303030201
514304300141
61511230305
7315661256
oct107631441
938366735
1018821921
11a696208
126378395
133b90141
1426dd42d
1519bbceb
hex11f3321

18821921 has 2 divisors, whose sum is σ = 18821922. Its totient is φ = 18821920.

The previous prime is 18821903. The next prime is 18821923. The reversal of 18821921 is 12912881.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18800896 + 21025 = 4336^2 + 145^2 .

It is a cyclic number.

It is not a de Polignac number, because 18821921 - 26 = 18821857 is a prime.

Together with 18821923, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (18821923) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9410960 + 9410961.

It is an arithmetic number, because the mean of its divisors is an integer number (9410961).

Almost surely, 218821921 is an apocalyptic number.

It is an amenable number.

18821921 is a deficient number, since it is larger than the sum of its proper divisors (1).

18821921 is an equidigital number, since it uses as much as digits as its factorization.

18821921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2304, while the sum is 32.

The square root of 18821921 is about 4338.4237921162. The cubic root of 18821921 is about 266.0038865394.

The spelling of 18821921 in words is "eighteen million, eight hundred twenty-one thousand, nine hundred twenty-one".