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21091389 = 311297599
BaseRepresentation
bin101000001110…
…1010000111101
31110200112221120
41100131100331
520344411024
62032021153
7344162634
oct120352075
943615846
1021091389
11109a6300
1270917b9
1344a6117
142b3051b
151cb9479
hex141d43d

21091389 has 24 divisors (see below), whose sum is σ = 31281600. Its totient is φ = 12629760.

The previous prime is 21091361. The next prime is 21091409. The reversal of 21091389 is 98319012.

It is not a de Polignac number, because 21091389 - 213 = 21083197 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21091319) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34912 + ... + 35510.

It is an arithmetic number, because the mean of its divisors is an integer number (1303400).

Almost surely, 221091389 is an apocalyptic number.

It is an amenable number.

21091389 is a deficient number, since it is larger than the sum of its proper divisors (10190211).

21091389 is a wasteful number, since it uses less digits than its factorization.

21091389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 721 (or 710 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 21091389 is about 4592.5362274020. The cubic root of 21091389 is about 276.2920532746.

The spelling of 21091389 in words is "twenty-one million, ninety-one thousand, three hundred eighty-nine".

Divisors: 1 3 11 33 97 121 291 363 599 1067 1797 3201 6589 11737 19767 35211 58103 72479 174309 217437 639133 1917399 7030463 21091389